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Archive 1Archive 2Archive 3

WikiProject Time assessment rating comment

Want to help write or improve articles about Time? Join WikiProject Time or visit the Time Portal for a list of articles that need improving.
—Yamara ✉ 08:45, 18 February 2008 (UTC)

UTC discussions not in support of this article

It took me months to figure out that the Recent Changes page bases its clock on UTC. Several times I've been tempted to send an email to Jimbo asking him to reset the Wikipedia internal clock. If others have been confused and considered this a minor annoyance, then I'd like to suggest that the term (UTC) be added to the timestamp on the Recent Changes page. -- Modemac 20:10 Feb 8, 2003 (UTC)

Worth doing; note that you can change the timezone used to display times in your preferences. (Another possibility is to use JavaScript (yuck!) to display times in the reader's local timezone.) --Brion 20:22 Feb 8, 2003 (UTC)
Thanks to your suggestion, I figured out how to set my Wikipedia settings to match my time zone. Rather than adding some fancy code, why not just put a tiny addition to the Recent Changes page so that it looks like this:
Below are the last 250 changes in last 7 days.
Show last 50 | 100 | 250 | 500 changes in last 1 | 3 | 7 | 14 | 30 days.
Show new changes starting from 16:02 Feb 8, 2003 (UTC)
-- Modemac 21:04 Feb 8, 2003 (UTC)
I see the UTC time and cannot see my local time, although I have change the settings. So a link to UTC clock when the time appear in UTC it´s very usefull ( internal or external link ). I can suggest a lot of sites.

Discussions on how the article should develop

The following sentance in the article makes little sense to me, since no reference date is given:
"As of 1 January 1999, TAI is ahead of UTC by 32 seconds."
Over what period of time was 32 seconds lost? < /br> wamquark< /br> Sunday, November 27, 2005, 12:36:42 PM EST

I am adding 1 January 1958 to the article. — Joe Kress 18:50, 29 November 2005 (UTC)
"As of" usually means "since that moment until now (when you just read this)", so the reference date you seek in the sentance (sic) is whenever you read it - hope that makes sense now. Incidently, it now reads "As of 31 December 2005, TAI was ahead of UTC by 33 seconds" with additional information (good work, Joe Kress!) as to when each of those 33 seconds were added. 07:03, 1 January 2006 (UTC)

I've removed the above links, as they don't describe UTC in any useful way. They seem to be about an obscure date/time formatting specification which, as it happens, may use UTC as the timezone. --Brion 12:12 Feb 9, 2003 (UTC)

W3C have UTC date and time standards. They are interesting to use in the Internet. Where place them relating to UTC and include a link in UTC??. Perhaps UTC web or UTC Internet??
"This document is a NOTE made available by the W3 Consortium for discussion only. This indicates no endorsement of its content, nor that the Consortium has, is, or will be allocating any resources to the issues addressed by the NOTE." It's not a w3c standard, and UTC is only barely touched upon as the base timezone that others are offset from. Frankly I see no reason to link it from anywhere in the Wikipedia. --Brion 13:10 Feb 9, 2003 (UTC)

From http://www.ietf.org/internet-drafts/draft-ietf-impp-datetime-05.txt

This document defines a date and time format for use in Internet protocols that is a profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar

So, ISO 8601 it´s a standard. And the rest are proposed profiles of the standard in the Internet. Very important for people that uses UTC, specially in the Internet.

Because of this I propose include a link to UTC(Internet). If interesting for the user, the user will deciede clicking in the link ;)

Regards

I have translated the UTC article into Spanish ;)

Mac

stronger statement re UTC abbr origin

Why "UTC"?
Putting stronger language into the article abt this is low among my prioriies. --Jerzy 23:03, 2003 Dec 15 (UTC)

Range of UTC times

Article should say whether UTC implies 24-hour format. And in any case, whether format is specific as to range:

  • 0:00 to 23:59,
  • 0:01 to 24:00, or
  • 1:00 to 24:59

(or their 12-hour equivalents) --Jerzy 23:14, 2003 Dec 15 (UTC)

The term UTC may not formally imply any particular notation, but in practice, UTC is everywhere shown using the 24-hour notation defined in ISO 8601, which counts the seconds of a day from 00:00:00 to 23:59:59 (23:59:60 in case of a leap second). That is world-wide simply the most commonly used time notation. (The question probably only arises in the few countries where a different time notation is still commonly used.) Markus Kuhn 13:54, 25 July 2005 (UTC)

This is correct. A whole moment of time begins at zero, and ends on the fullest point before 1. This is 0.9999999. The statement below was in the link above. This is wrong. For by the logic here, if the beginning of the 2nd millenium was 2001, the beginning of the 3rd millenium will be 3002. Just thought Id point this out. Zero hour is a mysterious point in time, yet is is definitely on the AM, rather than the PM. Our midday begins the night and midnight begins the day. Interesting.

When did the current millennium begin?

Since a millennium is 1000 years, and the first millennium began at the start of the year 1, it ended at the end of the year 1000. The second millennium then began with the year 1001 and concluded at the end of the year 2000. Therefore, the current millennium technically began with the year 2001. For historical information, see an exhibit on Calendars.


This statement was found here. Why "UTC"? We truly cannot always use the internet to source articles on the Wiki. Time is a difficult concept to grasp though.

WikieWikieWikie (talk) 23:21, 7 August 2008 (UTC)

Placement of table

The table of conversion from UTC appears so far to the left that the Special Pages links cover part of it. I'm in Cologne Blue, 1024x768 with a fixed left sidebar - anything we can do about this unsightliness? -- Rissa 19:48, 4 Jun 2004 (UTC)

I've floated the table to the right and tightened the width a bit so page the page flows better. Garglebutt / (talk) 07:31, 13 September 2005 (UTC)

DST

It should be noted that in DST there is a different UTC -/+ time (E.g in winter, CST is UTC-6 while in Summer it is UTC-5...slightly annoying for me actually [considering WP is UTC]). Ilyanep 02:12, 21 Jun 2004 (UTC)

CST is always UTC-6. In Summer, most people in CST change to CDT, which is UTC-5. 21:12, 11 April 2006 (UTC)

Zulu time

Quaint mention "also referred to as Zulu time". A bit of explanation might raise the human interest of the page...I'd never even heard of UTC (AFAIK everyone still uses GMT in the UK)--BozMo|talk 15:37, 19 Aug 2004 (UTC)

http://www.grc.nasa.gov/WWW/MAEL/ag/zulu.htm

(The standard is coordinated universal time, abbreviated UTC. This was formerly known as Greenwich mean time (GMT). UK uses GMT/BST/IST) "Zulu" is just one of 25 designations that NATO and US Military uses.)

I've added a short sentence to try to clarify the meaning of Zulu time, and a link that has a good summary of the Alpha-Zulu time zones, listing some key locations worldwide. Of course, the time zone can change when a country uses a daylight-saving time. For example, in winter the UK uses GMT/UCT, i.e Zulu time; in summer it moves to British Summer Time (BST), which is one hour ahead, i.e Alpha time.--RDT2 13:19, 18 June 2006 (UTC)

The US Navy uses "Zulu" for UTC. Do other services? Other nation's militaries? Gerardw (talk) 19:32, 21 September 2008 (UTC)

Need for disambiguation

There should be a disambiguation section added, since the letters UTC form the initials of the University of Tennessee at Chattanooga. --ZekeMacNeil 23:13, 10 Jan 2005 (UTC)

Done. Joe Kress 07:21, Jan 11, 2005 (UTC)

Removing protection

An extensive discussion regarding the Time Cube edit war has been taking place at Talk:Greenwich Mean Time#Time Cube discussion. I hope the issues have been resolved for now and am unprotecting this page. — Knowledge Seeker দ 20:40, 2 May 2005 (UTC)

Merger with UT

The merge on this and UT seems a bit silly. They are different and warrant different articles. Whoever put the notices on hasn't said why they think they should be merged either. If nobody gives any reasons then I'll just take the notices off. KayEss | talk 09:05, 28 December 2005 (UTC)

  • There is significant duplication between these articles. But still, I'm sceptical about the merge. While they both include information on UTC, the focus is different Coordinated Universal Time presents UTC as a civil time reference, and goes on to describe other timezones. Universal Time describes UTC as one of the various UT timescales and discusses the derivation of these timescales. Segv11 (talk/contribs) 11:22, 28 December 2005 (UTC)
I've removed it from the two pages. If anybody has good reasons for still merging then don't hesitate to speak up. KayEss | talk 05:41, 30 December 2005 (UTC)

UT vs GMT

Although the scientific discussions concerning Universal time etc are no doubt important and valid it should be made clear that the people of the world generally and all broadcasters etc use Greenwich Mean Time and not Universal Time. The simple fact is that these are of course identical, each starting from Greenwich London England. The only real reason Universal Time and its variants Zulu Time etc is used is because of irritation at Britain still being the place from which the world takes its time. If people are honest they will admit this..

The problem with non scientific people using "Universal Time and its variants is obvious... If the time is UNIVERSAL then it must be the same EVERYWHERE!! So.. if its 0900 in Paris it must be 0900 in New York! As this is impossible you have to do a calculation..and for other places? Well of course UTC is really the time at a place called Greenwich in England! so we have returned to GMT.!!. GMT will never vanish because it is much easier for people to visualise time zones when they have a real place in the world from which to start... It may give some people a thrill at stamping on those pesky British but it wont work you know.. You could help the world just a little bit by promoting GMT and making life easier for everybody!!! —the preceding unsigned comment is by 80.98.112.51 (talk • contribs) 19:14, 2 January 2006 (UTC1)

Universal Time is indeed the same everywhere, hence its name. It is a single time useable for the entire world whenever it is appropriate, for example, when timing celestial events like solar eclipses or earthly events like earthquakes. Time signals broadcast by WWV and all other national time radio services are always given in Coordinated Universal Time, even though WWV, for example, is in Fort Collins, Colorado, USA and thus by your argument, should broadcast only Mountain Standard Time. — Joe Kress 07:35, 5 January 2006 (UTC)
UTC != GMT... at least not if you care about seconds. The article explains this. GMT is an (unspecified) mean solar time at the Prime (Grenwich) Meridian. UT0 and friends are various ways of regularizing this concept in the face of the Earth's rotational irregularities. TAI is an artificial (but predictable) timescale based on atomic clocks, and UTC is a compromise between UT0 and TAI... Segv11 (talk/contribs) 08:22, 5 January 2006 (UTC)
I suggest to read Discussion of the article Prime Meridian.--Fev 04:11, 22 February 2006 (UTC)
All I want to know is, if someone has edited a wikipedia discussion page and put "22:06, 1 October 2006 (UTC)", what time is that in my country? I have spent about ten minutes reading this page but I am not sure yet, and I am too lazy to keep trying. I suspect that many people only read this page for the same reason. How about, near the top of this article, I put something like "UTC is not exactly identical to GMT but to most practical purposes they are the same thing; so if the UTC time is 14:51, it is xx:51 in Tokyo, xx:51 in Chennai, xx:51 in London and xx:51 in California". If people agree I'll sort the times out and put something about BST too. Chorleypie 22:14, 1 October 2006 (UTC)
That is extraneous information which only duplicates the information in List of time zones which is indicated as a main article under UTC#Time zones. A more explicit statement that the information you desire is located in List of time zones would be appropriate. — Joe Kress 06:49, 3 October 2006 (UTC)
I think it's highly practical information. That's what I came here looking for too. I'd put it in except that the article currently seems to be an exercise in confusing people, and it's just succeeded. I don't want to perpetuate misinformation. Njál 00:56, 12 October 2006 (UTC)
To clarify, I don't think the string of countries is necessary. GMT is sufficient, if it includes a mention of summertime, as people don't start referring to their timezone as BST just because the government decides to play with time. Njál 01:10, 12 October 2006 (UTC)
Do Not Merge UTC ≠ GMT. This is not an argument about seconds, but the equation as to how why and how those seconds differ. Autopilots 07:13, 17 September 2006 (UTC)

I believe GMT changes with daylight savings time and UTC does not. Am I wrong about this? mike 18:06, 28 September 2006 (UTC)

Neither UTC nor GMT changes with daylight saving time. GMT with daylight saving time is called British Summer Time. For the official perspective of the Royal Observatory, Greenwich see Summer Time. — Joe Kress 20:56, 29 September 2006 (UTC)
And does UTC have its own arcanely-named alteration according to the seasons, or does it stay the same all year? I'm assuming that for all practical purposes (the ones conspicuously lacking in this article) daylight saving time has the same function and effect as BST — do inform me if I'm wrong, of course. Njál 00:56, 12 October 2006 (UTC)
It's amazing, the lengths the Americans will go to, to avoid admitting that Europeans got to anything important first (such as time or stamps)...Deipnosophista 20:43, 15 May 2007 (UTC)
What's amazing is how little Europeans know about world history BEFORE Europe (sounds like the argument Europeans like to make about the Americans, doesn't it?) In case you have forgotten, here's a little history: sometime before 2000 BC the Sumarians (they lived in what is now Iraq, which has never been anywhere near Europe) had developed a system of time with 60 seconds in a minute, 60 minutes in an hour and 12 hours of day and of night. They even used a 12 month calendar. Sound familiar? And the Egyptians (ditto, non-Europeans) were using sundials by day and water clocks by night by about 1500 BC. Europeans did eventually further refine calendars, time-keeping systems and the concept of time, but they did not get to them "first". --Blake the bookbinder (talk) 10:23, 21 June 2008 (UTC)
Your Sumerian history is mostly incorrect (they did use a 12-month year plus an intercalary month). Although the Sumerians and Babylonians did use a sexagesimal (base sixty) number system, they only subdivided the day sexagesimally. They did not use our hour, minute, or second. Their smaller time units were the double-hour (two or our hours), the time-degree (four of our minutes), and the barleycorn (3⅓ of our seconds). The subdivision of the day into 24 hours was due to the ancient Egyptians (12 hours of day and 12 hours of night). Hipparchus and Ptolemy changed this to 24 equal (or equinoctial) hours in a nychthemeron (night+day). The further subdivision of the hour into 60 minutes, that into 60 seconds, etc. is due to Muslim scholars (see second#history). — Joe Kress (talk) 20:35, 23 June 2008 (UTC)
WELL! You learn something new every 23.934 hours (or so). Many thanks for the news from Sumer (and for pointing out the important early, pre- or non-European contributions of the Babylonians, the ancient Egyptians and Muslim scholars to the development of time-keeping as we know it today). --Blake the bookbinder (talk) 09:03, 28 June 2008 (UTC)

I think there's a point to the above comment which asks how does UTC relate to local time and to GMT. I think it is true that UTC and GMT will never differ by more than a second, and that the differences are really important for, say, astronomic observations, and as a legal standard. --Ozga 05:36, 26 May 2007 (UTC)

United States laws regarding time zones (15 USC 261) do not mention UTC, only "mean solar time … west of Greenwich" at several meridians. Thus US time zones are legally referred to GMT, not UTC. Nevertheless, UTC is broadcast by WWV and is the official US time. So in the US, UTC is official but not legal. The same situation applies in many other countries. Furthermore, UTC has been the official time broadcast by the US and UK since 1 January 1960, by virtually all national time services since 1963, and officially acquired the name "Coordinated Universal Time (UTC)" in 1965. But its time was steered to match GMT within 0.1 second by making all seconds slightly longer than an SI second—it was atomic time with a specified frequency offset. On 1 January 1972, all seconds became exactly one SI second long and periodic leap seconds were implemented to keep UTC within 0.7 seconds of GMT (increased to 0.9 seconds in 1974). For this history see "The leap second: its history and possible future" (PDF). (381KB). In 2005, it was officially proposed that leap seconds be abandoned in favor of leap hours (basically, section 11.1(7) in the reference)—but that proposal failed, or at least it has been tabled for the time being. See Leap second#Proposal to redefine UTC and abolish leap seconds. — Joe Kress 08:33, 26 May 2007 (UTC)
Thanks, Joe. I appreciate the correction. --Ozga 16:07, 26 May 2007 (UTC)
Oh but wait, if you ever get back to this section, to be clear, that our logs dated in UTC may be off by 0.9 seconds for legal purpose? E.g. A log entry showing activity 0.1 second after midnight UTC might not be an infraction of a ban which goes into effect at midnight (legal time)? --Ozga 02:52, 28 May 2007 (UTC)

In general common usage UTC is identical to GMT and this article should clearly state that right at the top! On my PC I have GMT listed as a time zone but no UTC, and then I receive an email with a UTC time and I wonder if UTC is the same as GMT? Then I come to Wikipedia to find out. Many will go through this process and you should tell us what the answer is. Of course they are effectively the same but your article doesn't clearly state that at the top, for petty technical reasons. I tried to add it in but some pillock removed it. When are you wikipedia editors going start thinking about your readers and use some common sense? GMT has various meanings but the commonest is UTC (atomic clock based), and the main other GMT meaning, based on astronomy, differs at most by 0.9 of a second from UTC. Very few people use the latter meaning anymore. There is an article here that explains it in detail "http://www.apparent-wind.com/gmt-explained.html". Retrieved 2007-08-19. {{cite web}}: External link in |title= (help). --190.76.7.166 02:22, 20 August 2007 (UTC)

Given that UTC is a French inception the original editors remarks that it was utilised as an anti-English reliance having to cite Grenwich as the center of the chronological earth is correct. The only countries I have found use UTC in any open forum are France and America. That being said, 99% of publications of time are in GMT even IN those countries. I see UTC only on Wikipedia, throughout my travels around the world it's popped up once or twice, but mostly as an oddity. I find it very problematic that we at Wikipedia utilise UTC because it doesn't allow me to understand the time frame reference they're talking about exactly. GMT everyone understands. Fair enough they're 'near identical', but they're not and UTC is unreliably different and requires an understanding of the mathematical principals to deduce from a given time, I know that when it's midday here it's 2am at Grenwich and from that I can deduce (exactly) all other time lines around the world.

I turned to Wiki to find out what Pacific Standard Time is and it has, for the first time ever, truly failed me as a resource to be able to work out the time difference. I'd say perhaps we should move to GMT like the rest of the world, but given the different target audience that Wikipedia has, I doubt that would go down well for the most part. 210.49.15.52 13:05, 13 November 2007 (UTC)

Standards

Following the ISO standard one have to include T to separate date and time in UTC format. The Z to indicate zulu time (zero time) is not necessary. --82.159.136.238 05:54, 20 April 2006 (UTC)

The standard allows a T to be inserted between date and and time parts if they are stored in one data field, but this is not mandatory and it may be replaced by a blank. It is common practice to use the blank in human presentation. And it certainly does not make sense to use an italic T in a computer field. The Z is the official indicator to show that UTC time is meant. −Woodstone 07:34, 20 April 2006 (UTC)

merge from leap second

Leap seconds are solely a feature of UTC, and UTC cannot be defined without discussion of leap seconds. They form a single topic, so it is silly for them to have separate articles. 81.168.80.170 12:15, 29 April 2006 (UTC)

To me, it seems the articles are shaping well as they are. As it is, leap second is a sub-topic of UTC. Because the leap second is a detail, it shouldn't be discussed too much in the UTC article; because it is interesting, it warrants an article in Wikipedia elsewhere. --TuukkaH 20:26, 29 April 2006 (UTC)
This is an encyclopedia article intended for those who do not understand the topic. These people do not realize that UTC has leap seconds, so they will be confused if they are redirected from leap second to UTC. The articles should not be merged. — Joe Kress 12:05, 14 May 2006 (UTC)

Sandford Fleming

Sandford Fleming was the inventor of Universal Standard Time. He proposed linking of Time Zones to the 180º Meridian in the 1884 International Meridian Conference. Why this fact is not registered here?. --Fev 22:10, 14 May 2006 (UTC)

Why is it abreviated that?

Why is it abreviated that? It's Coordinated Universal Time, not Universal Time Coordinated. Why UTC, it should be C.U.T. --71.224.19.29 16:16, 25 May 2006 (UTC)

Read the article. It's explained in the second paragraph. — Joe Kress 05:51, 26 May 2006 (UTC)
No, it's not. Maybe it was in 2006, but it's not now, and I have the same question. 138.78.98.104 (talk) 15:13, 29 September 2008 (UTC)
See Coordinated Universal Time#Abbreviation. Not everything can be in the lead. --Wtshymanski (talk) 15:49, 29 September 2008 (UTC)

UT1 definition

Could someone define the meaning of UT1 before using it in the article? It would help in understanding the concepts.

Thanks —Preceding unsigned comment added by 206.173.170.67 (talk • contribs)

That would be a little difficult because UT1 has a rather complicated definition, which if stated would make matters worse. (UT1 is UT0 corrected for polar motion. UT0 is UT at a particular observatory.) Probably better would be to say that it is Greenwich Mean Time (in its old pre-1960 sense). In that sense it is indistinguishable from UT. But saying UT1 is the same as GMT is incorrect because in modern British usage GMT has leap seconds. For now, I'll relie on the purpose of its hyperlink, UT1, which is there to provide its definition for those who do not know it. — Joe Kress 04:07, 31 May 2006 (UTC)
I've added "equivalent to GMT before 1960". — Joe Kress 03:44, 20 June 2006 (UTC)

I believe the UTC article shouldn't be merged with GMT

For heaven's sake, they are completely different things. Why propose this merger in the first place is what I'm wondering.--Saoshyant 11:01, 9 October 2006 (UTC)

Absolutely. I come here, looking for a quick factoid, and find Wikipedia has gone crazy in my absence. *mind boggles* Njál 00:45, 12 October 2006 (UTC)
I agree, they definitely shouldn't be merged. They are completeley different. What are the reasons for merging??? caesarsgrunt 23:10, 16 October 2006 (UTC)
I removed the merge notice. No reasons where pointed out for the merge.--Ivo Emanuel Gonçalves/Saoshyant talk / contribs 14:37, 20 October 2006 (UTC)

simple explanation needed

Okeh, I know it's a technical term, but instead of burying the key sentence (for the average user) at the bottom of the first or second paragraph, couldn't we some-how make it easier to see that UTC is (for many purposes - e.g., use on Wik) GMT? Kdammers 00:39, 11 March 2007 (UTC)

Proposed Clarification of a paragraph in Mechanism

In the following paragraph: Most UTC days contain exactly 86,400 seconds, with exactly 60 seconds in each minute. However, since the mean solar day is slightly longer than 86,400 seconds, occasionally the last minute of a day will have 61 seconds. (If a UTC day were to have 86,399 or 86,401 seconds, the last minute of the day would have 59 or 61 seconds, respectively, but this has never happened). The irregular day lengths mean that fractional Julian days do not work properly with UTC. The intercalary seconds are known as "leap seconds".


Logically, the statement If a UTC day were to have 86,399 or 86,401 seconds, the last minute of the day would have 59 or 61 seconds makes sense, however with the explanation that a solar day is slightly longer than 86,400 seconds statement above, the time reference there leads me to believe that the bolded statement is wrong, technically, because it doesn't reference that occasional adjustment in the same paragraph. I inevitably am wrong, but I suggest making the two points more clear.

Proposed Revision: Most UTC days contain exactly 86,400 seconds, with exactly 60 seconds in each minute. However, since the mean solar day is slightly longer than 86,400 seconds, occasionally the last minute of a solar day will have 61 seconds. If a UTC day were to have 86,399 or 86,401 seconds, the last minute of the solar day would have an adjustment of one, in each respective direction, however this has not happened to date. The irregular day lengths mean that fractional Julian days do not work properly with UTC. The intercalary seconds are known as "leap seconds".

I'm not sure if my change is better, but it clears up my confusion. Musikgoat 08:37, 6 September 2007 (UTC)

The statement "the last minute of the day would have 59 or 61 seconds, respectively, but this has never happened" is indeed wrong because 61 seconds occurs every time a leap second occurs. It is 59 seconds which has never happened, although it is allowed by the IERS should the Earth ever rotate slightly faster. The specific kind of second (SI) needs clarification, which is your concern. I'm correcting the paragraph. — Joe Kress 05:08, 7 September 2007 (UTC)

Erronous?

what i´m wondering is how "Universal Time Coordinated" is errounous. as far as i can udnerstand it, the article first sais that UTC is Universal time with Coordinated added and then it sais it´s been errounously expanded into "Universal Time Coordinated" Psilorder 21:44, 11 September 2007 (UTC)

got it after a bit of consideration, would be nice if the article said it outright however.

that they didnt settle on naming it something that abbreviates to UTC, but simply to move around the letter in the abbreviation.

Psilorder 21:51, 11 September 2007 (UTC)

[[ hopiakuta Please do sign your signature on your message. ~~ Thank You. -]] 07:00, 1 January 2008 (UTC)

UTC utc cut CUT Universal_Time_Coordinated_ wiktionary : emplacement

  • @ "cut" is:

Phrases starting with cut:

"...procedure for change data emplacement,..." seems poorly worded; I cannot translate it.



How did that get there?

Why did it get there?

Who did it?

What sort of code would do that?

Does it provide any perspective? How?

Does it relate to Greenwich, Greenwich_Mean_Time, Universal_Time, somehow?

[[ hopiakuta Please do sign your signature on your message. ~~ Thank You. -]] 07:00, 1 January 2008 (UTC)

Joe Kress (talk) 03:32, 2 January 2008 (UTC) provided the following answer:
The phrase "...procedure for change data emplacement,..." in Cut is indeed poorly worded. I'm changing it to "procedure for editing text".
I'm not sure what apparently irrelevant link you are referring to.
The phrase Redirected from UTC appears immediately below the article's title, "Coordinated Universal Time", if you type "UTC". This allows editors to change the redirect if they determine it is inappropriate. But editors have determined that in this case most readers who type "UTC" do want information on "Coordinated Universal Time". In case a reader does not, he is directed to the page entitled UTC (disambiguation), which lists other Wikipedia articles that can be abbreviated "UTC". Both phrases appear at the top of the article so that a reader does not have to read the entire article just to find some other "UTC". Wikipedia calls this process disambiguation.
Both at the beginning and end of this comment I entered my Wikipedia:User name and time/date by typing four tildes, "~~~~". The Wikipedia software automatically replaced the four tildes with my Username and the time and date. — Joe Kress (talk) 03:32, 2 January 2008 (UTC)

Displayed time is wrong

I just had a look at the article, and it stated close to the top: 

   Example: Thursday, 2008-01-31 14:05 UTC
   This was the actual time in UTC when you loaded this page

While the date is correct, the time is off by more than 7 hours, as it was actually more like 21:35 UTC. I'm in central Europe, and the time was 22:35 CET. Maybe there is some sort of caching going on on the Wikipedia server? If so, either that should be disabled for this page if possible, or the "current time" gimmick should be removed.

That is precisely why it says: "This was the time ... ". −Woodstone (talk) 21:47, 31 January 2008 (UTC)

UTC is only determined for the past. Not for the future or even the recent past.

As I understand it, UTC is determined with hindsight. An institute in France determines the exact UTC time some time afterwards. The time is determined using about 300 atomic clocks spread over the world, this information is accumulated from these clocks the actual UTC is determined. Each of the locations get then a report how much that clock was off from the determined UTC time. As I understood this process takes weeks. So owning an atomic clock you get reports afterwards so the correct time is known but only for clock times a few weeks in the past. So UTC actual can only be used for events which are allready in the past by some weeks.

Offcourse for most practical uses, even when using atomic clocks this 'small' correction is not needed. Crazy Software Productions (talk) 14:15, 1 March 2008 (UTC)

Your statement is correct for TAI, where the correction is in microseconds. But UTC is TAI with a few leap seconds added. Leap seconds themselves are determined for the future (by almost six months), the opposite of for the past. — Joe Kress (talk) 03:15, 2 March 2008 (UTC)
Actually, Crazy Software Productions' statement is correct, if I understand it correctly. If a person had access to the United States Naval Observatory master clock, and timed an event with that clock to the nanosecond level, he would have to later correct the time to the real UTC when the correction became available. A list of such corrections for various modified Julian dates is available at http://tycho.usno.navy.mil/TAIMC2.DAT (the second column is the correction, in nanoseconds). Few people have access to a time source with an accuracy to a few nanoseconds, so the correction is seldom useful. --Gerry Ashton (talk) 03:57, 2 March 2008 (UTC)
I said "Leap seconds themselves". Leap seconds are predicted. The TAI basis of UTC and hence UTC itself does require nanosecond correction, but its leap seconds do not require correction. — Joe Kress (talk) 04:32, 4 March 2008 (UTC)
Since TAI and UTC differ by an integer number of seconds, any correction to TAI is also a correction to UTC. --Gerry Ashton (talk) 04:37, 4 March 2008 (UTC)
As I understand it TAI is used for example in GPS, the corrections (for UTC) which are only available weeks after the event, can not be used at the actual time. So I assume that these corrections are not included in TAI, where for official UTC they are used. (But only quite a large time after the event.) If TAI does contain these corrections, then what is the name of the time without the corrections. (As used for example by GPS).Crazy Software Productions (talk) 16:32, 4 March 2008 (UTC)
For a description of GPS time, see http://tycho.usno.navy.mil/gpsinfo.html#st
Since exact UTC is only known retrospectively, approximations to UTC are designated by putting the source in parenthesis, such as UTC(USNO). Naturally, if an approximation to UTC is known, the same approximation to TAI can be found by adding the accumulated leap seconds to UTC (currently 32). --Gerry Ashton (talk) 17:55, 4 March 2008 (UTC)

Zulu time != UTC

UTC is also referred to by the military and civil aviation as Zulu time (Z).

The reference given for the above statement only had one line evoking any correlation between UTC and Zulu, that being:

NOAA satellites use Zulu Time or Coordinated Universal Time (UTC) as their time reference. The satellite images that appear on NOAA's Web sites are stamped in Zulu time.

The conjunction of 'or' lacks a comma before it, meaning it is used to indicate an alternative, usually only before the last term of a series, if there were a comma before it can be used to indicate a synonymous or equivalent expression. As illustration, 'this or that' is different to 'acrophobia, or fear of great heights.' Noticably so. The fact this entire thing was sourced based on a missing comma is disgusting.

UTC and GMT are identical with minor differences in seconds. Thus only in instances where extreme accuracy is required do we find it implemented. The above error in logic led me to scroll down to the Uses section, which was even more abhorrent. I shall address each section specifically as I excised them due to flawed logic.

Those who transmit on the amateur radio bands often log the time of their radio contacts in UTC, as transmissions can go worldwide on some frequencies. In the past, the FCC required all amateur radio operators in the United States to log their radio conversations.

By commenting on FCC regulations in relation to LOGGING CONVERSATIONS that statement attempts to draw legitimacy to an unsourced claim that UTC is used. In twenty years of amateur radio operation I've never heard anything but GMT used.

Some watches include a second 12-hour display for UTC.

Yeah? Irregular leap seconds sent out as updates. High tech watch, or psychic powers. I think not.

UTC is also the time system used in aviation, referred to as Zulu.[1] Weather reports, flight plans, air traffic control clearances, and maps all use UTC to avoid confusion about time zones and daylight saving time.

Bzzt, debunked above.

UTC is the time system used for many Internet and World Wide Web standards. In particular, the Network Time Protocol, which is designed to synchronize the clocks of many computers over the Internet (usually to that of a known accurate atomic clock), uses UTC.

NTP uses Marzullo's algorithm with the UTC time scale, including support for features such as leap seconds. NTPv4 can usually maintain time to within 10 milliseconds (1/100 s) over the public Internet, and can achieve accuracies of 200 microseconds (1/5000 s) or better in local area networks under ideal conditions.

NTP does NOT use UTC as a standard, it uses UTC and Marzullo's algorithm to compute a standard far more precise than GMT or UTC as a whole.

For most common and legal-trade purposes, the fractional second difference between UTC and UT (GMT) is inconsequentially small, so UTC is commonly called GMT

The above paragraph has been changed to:

For all non-scientific purposes, the fractional second difference between UTC and GMT is inconsequentially small, so GMT is predominantly used

There's two more paragraphs left which could be merged into the bloody body. So so far, this UTC article has been nothing but puff and bollocks. Come on people, get it together. 122.107.42.146 (talk) 05:09, 27 March 2008 (UTC)

I have reverted 146's edits because I do not believe that GMT is predominant over UTC. For applications where a difference of one second or less is unimportant, GMT, UT, UT1, UTC, and Z all indicate the same time scale. Where is the proof that GMT dominates all these other abbreviations?
Also note that in the United States, civil time in all the time zones now differs from UTC by an integer number of hours; the phrase "Coordinated Universal Time" is specifically used in the law. --Gerry Ashton (talk) 18:30, 27 March 2008 (UTC)

Relationship of GMT and UTC

A plea to regular editors of this page: make sure it's always crystal clear that for non-technical purposes, UTC is the same as GMT.

I like detailed scientific discussions. I spend much of my life writing them. But that's not the only purpose of this page. Many people come here because they read a wikipedia page saying "such-and-such occurred at 11:23 UTC", think "what on earth is UTC?", and type "UTC" into the search box. All they want to know is that UTC is — for these purposes — what they know as GMT. That's all. And that information should leap out at them. It shouldn't take more than five seconds for a casual reader to find that information and move on.

In mid-March there was a nice clear paragraph stating that in one line. Since then that paragraph has got progressively more technical. I repeat: I have nothing against technicalities. But please, set aside one tiny part of the introduction for readers who wish to avoid them. 86.0.204.154 (talk) 01:44, 5 April 2008 (UTC)

Well, it took three minutes for my edit to be reverted. I'm not going to fight. If anyone really thinks that the sentence "Leap seconds allow UTC to closely track UT1, which is mean solar time at the Royal Observatory, Greenwich" quickly conveys to the non-technical reader that for most everyday purposes, UTC is the same as GMT, then... it's beyond me. 86.0.204.154 (talk) 01:55, 5 April 2008 (UTC)
I don't oppose the concept of a short message in the introduction explaining the similarity of GMT and UTC. However, I'm not happy with saying they are the same for non-technical purposes. To me, non-technical only refers to the maximum time difference. But there are other factors:
  • UTC is recognized by law, and specific agencies are authorized to compute and disseminate it. GMT is no longer recognized in US federal law for civil timekeeping, and I understand that's also true in the UK. There is no official source for GMT. The legal status of GMT is less certain than UTC.
  • Before 1925, GMT was reconned from noon, not midnight. Granted, UTC didn't exist back then, but there was an overlap of UT and GMT, so saying they are the same could lead to problems for historians.
  • The term GMT is distained by the technical community due to its ambiguity; UTC is approved. By telling readers they are the same for non-techncal users, we are exposing those of our readers who also write to the distain of the technical community.
Furthermore, the new paragraph and the paragraph that followed it were disjointed and verged on contradicting each other. --Gerry Ashton (talk) 02:00, 5 April 2008 (UTC)
One minor point: Astronomical GMT and nautical GMT did begin at noon before 1925, but civil GMT, ever since it began sometime before 1840, has always begun at midnight. See resolution 5 of the 1884 International Meridian Conference. This disagreement resulted in resolution 6 expressing the hope that the astronomical and nautical forms also begin at midnight. Thus I support any wording that avoids discussing these historical convolutions of GMT in an article where GMT is not the subject. — Joe Kress (talk) 04:26, 6 April 2008 (UTC)

Racism

Isn't UTC anti-british pro-americanisation racism. Isn't this yet another prime example of the forced americanisation the world is going through at the moment. I say that GMT is more useful and UTC is a waste of some americanising idiots time and effort in thinking up this crap.--134.225.179.54 (talk) 11:49, 27 April 2008 (UTC)

GMT? More useful? How would you know? If you live in the UK you probably haven't come in contact with GMT since 1972 when the BBC pips, the nominally 'Greenwich' Time Signal, was switched to UTC. The pips themselves are timed by an atomic clock in the basement of Broadcasting House that is synchronised with the Global Positioning System (which is, of course, operated by the United States Department of Defense - at a cost of about 750 million dollars a year; one of the un-noticed examples of Americanisation).
UTC is calculated by the Bureau International des Poids et Mesures (headquartered in France with a French director ) so I don't know how your ideas on Americanisation (or, Americanization, even) apply here and since countries use UTC voluntarily, you are clearly wrong about the 'forced' bit. I won't bother to address 'racism', 'anti-British', 'idiots' and 'crap'.
You obviously feel very hurt and upset about something and I wish I could help. I'm sending good thoughts your way; I hope you can find peace of mind. --Blake the bookbinder (talk) 00:35, 12 May 2008 (UTC)

Under Refrenced?

This article is quite long and of a technical/scientific nature. 18 references seems a low number to me. Dose anyone else agree?--Talkshowbob (talk) 02:12, 19 May 2008 (UTC)

There are 5 general works in the bibliography, as well as the 18 citations to support specific parts of the article. The general works are quite good; I think the article is well-referenced. I don't see any cause for complaint; is there a specific passage that you think is doubtful and needs support? Or perhaps there is a passage you think a reader is likely to want further information about, for which we should supply a reference? --Gerry Ashton (talk) 03:25, 19 May 2008 (UTC)

Notice to Editors

It is important that a short introduction is added summarising the basis of UTC. UTC has evolved from GMT and it is imperative that unaware users from the UK and around the world understand this. After a small research study in the UK, I have learned that only a small proportion know what UTC is, whereas almost all understand GMT and still use it today. Therefore, a short sentence briefly summing up the comparison between GMT and UTC will suffice before going into the technical explanation which some users at first may not understand. Please feel free to discuss this. --AlexTheComposer (talk) 08:04, 31 July 2008 (UTC)

In what way is this statement from the article lead insufficient:

In casual use, Greenwich Mean Time (GMT) is the same as UTC and UT1. Owing to the ambiguity of whether UTC or UT1 is meant, and because timekeeping laws usually refer to UTC, GMT is avoided in careful writing.


I live in the UK and have done my own small research study (by which I mean I have, on occasion, asked my friends and colleagues what they know about UTC and GMT) and have found that the proportion of those who know anything about UTC is considerably less than "small"; I've yet to ask anyone who knows anything about UTC. Alex writes that "almost all [in the UK] understand GMT and still use it today" and he's half right - it's widely used, but rarely "understood". Many have the vague idea that it's, um, kind of, like, well the time in Greenwich (winter or summer) and/or that it's, um, the official time for the world and/or that it's the time you hear the pips pip out on Radio 4 each hour. People often know that the G is for Greenwich and the T is for Time, but less common are the people who know what the M is for and far fewer yet are those who know what it means (no pun intended). If people (the people I've asked, anyway) can use it correctly, it will invariably be as the designator of the time zone in which the UK is situated.
The comparison between (or, of) GMT and UTC is, I'm afraid, one of those things that is technical and off-putting to the casual reader (anywhere in the world) who doesn't want to spend much time on it (and especially to those who don't want to replace a national treasure with a cold, three letter acronym), but the biggest problem facing this wikipedia article is that there is no brief, and precise, summing up of the GMT/UTC relationship other than the unsatisfactory, "GMT is not UTC".--Blake the bookbinder (talk) 18:29, 31 July 2008 (UTC)
I have tried writing a revised introduction in my sandbox. Please let me know if you think it would be a suitable replacement, or if you can suggest any improvements. Note that I deleted the sentence "UTC replaced Greenwich Mean Time on 1 January 1972 as the basis for the main reference time scale or civil time in various regions" because the reference provided for that claim does not say that. --Gerry Ashton (talk) 19:30, 31 July 2008 (UTC)
The problem goes deeper than the intro. The explanation is confused. It states that UTC has discontinuities. That is not correct. UTC in seconds ticks at a steady rate. Only the mapping to days has irregularities. −Woodstone (talk) 19:59, 31 July 2008 (UTC)
The Mechanism section largely overlaps the History section, and I would say the History section is generally better written. Perhaps the Mechanism section should limit itself to describing how leap seconds are decided on, how the decision is disseminated, and the difference between the "paper" UTC scale and practical implementations such as UTC(NIST) or UTC(USNO)? --Gerry Ashton (talk) 22:11, 31 July 2008 (UTC)
I support Gerry and Blake on this. Gerry's test edit is a definite improvement because it states that GMT is the basis of UTC in the first sentence. However, there is one snag - I am not quite sure whether it is actually a replacement because in fact some Britons still use GMT. Some reworking is required but by collaborating and working together I believe that this can be solved --AlexTheComposer (talk) 20:17, 31 July 2008 (UTC)
The introduction goes on to say that "GMT" can be used to refer to either "UT1" or "UTC" in casual use. I would regard any modern use of "GMT" as casual, because correct terminology is not important enough to the people using it to look up how to do it right (or, the writer/speaker using "GMT" fears his/her/its audience is too ignorant to understand either UTC or UT1). --Gerry Ashton (talk) 21:15, 31 July 2008 (UTC)
After further reading it seems that "Greenwich mean time" might still be the legal name for the civil time observed during the winter in the UK and Channel Islands. Perhaps it has an equivalent legal definition in Ireland? In any case, I cannot discern whether the civil time is officially UT1 or UTC. (The United States didn't decide whether civil time was an integer number of hours offset from UTC or UT1 until 2007 by passing "H.R. 2272: 21st Century Competitiveness Act of 2007".) --Gerry Ashton (talk) 22:45, 31 July 2008 (UTC)
Yes, Gerry, Greenwich Mean Time (or in the summer it's GMT + 1 hour) is the legal time scale in the UK. If you went to court and got into matters where time really counted, they'd talk about things happening in GMT. The problem is that nobody has access to this time scale, we all use UTC (or its summer offset) here just like the rest of the world. So, just for fun, let's think about the unholy mess that's going to happen one of these days, when GMT (UT1) is .5 seconds ahead of UTC and I'm supposed to make a payment of £500 million to my bank by midnight or face a fine so large that it will cause the ruination of my business. The money leaves my account via computer at 23:59:59.7 UTC (which is the only time scale anybody uses, or even has access to). Even if it makes it to the bank the same tenth of a second that it left my account, legally, it's late. In law, GMT (UT1) counts; in life it's UTC we all go by. What a curious situation, no?
If you have not seen it before, have a look at Lord Tanlaw's 1997 attempt to get the UK to adopt UTC as its legal time scale, here [1] It failed. —Preceding unsigned comment added by Blake the bookbinder (talk • contribs) 23:21, 31 July 2008 (UTC)
I don't think Gerry's sandbox proposal says that GMT is the basis of UTC; at least I hope not. Apples are the basis of apple pie and, if anything, I would have thought that TAI is the basis of UTC since UTC is, in effect, TAI modified, as necessary, to closely track UT1. GMT (if by that you mean the mean solar time along the 1884 Prime Meridian) is the predecessor of UT1, but these days UT1 is defined without reference to the sun so it's wrong to say that GMT (even as UT1) goes into figuring UTC, at all. Peaches are not the basis of apple pie.
But Alex is right in that Britons (and others) do still use the term GMT; however, unless they are talking about the time zone, they are misusing it. The term they would use if they knew it is UTC. Can anybody tell me where I can get access to GMT (or UT1) without an observatory and a friend with a degree in astronomy?
Gerry, don't forget that leap seconds can be deleted as well as added (which is important if you are trying to define what UTC is, as opposed to what has happened to it in the past). While we're at it, let me throw in my draft attempt at a lead paragraph; it's concise and gives the basics without the history or details that can be given in the article (and it doesn't use French or mention GMT!):

Coordinated Universal Time is the time scale which is the basis of civil time around the world. It ticks along at the same rate as the ultra-consistent International Atomic Time (TAI) but is adjusted by leap seconds, when necessary, to keep it within 0.9 seconds of UT1, which is synonymous with the slightly inconsistent mean solar time along the Prime Meridian.

Let me sleep on discontinuities. --Blake the bookbinder (talk) 22:54, 31 July 2008 (UTC)
The problem is, it seems fundamentally unknown what the basis of civil time is in the UK and Ireland, if civil time needs to be known to a fraction of a second. Unless there is a law or decision I don't know about, this question won't be resolved until something bad happens and the highest court in these countries decides which time scale is the basis of civil time (or the Oireachtas or Parliament acts). --Gerry Ashton (talk) 23:57, 31 July 2008 (UTC)
Maybe I’m naïve but why is it “fundamentally unknown” whether civil time in the UK is GMT or UTC? Doesn't section 9 of the Interpretation Act 1978 cover it? --Mathew5000 (talk) 07:29, 1 August 2008 (UTC)
As for the Republic of Ireland, its legislation too defines time in terms of Greenwich Mean Time: section 1 of Standard Time (Amendment) Act, 1971 and section 18(i) of Interpretation Act 2005. Similarly, federal legislation in Canada defines time as a specified number of hours offset from Greenwich Mean Time (not UTC): see section 35 of Interpretation Act R.S.C.. --Mathew5000 (talk) 07:56, 1 August 2008 (UTC)
Let me suggest a senario. Bids are due on a huge UK contract on 30 November 2012 no later than 24:00, the bid notice says nothing else about the time. The lowest bid is received on 1 December 2012 at 00:00:00.2. It is rejected as late, but a lawsuit is filed. It comes out at trial that the computer receiving the bid was set to UTC, but 1 December 2012 at 00:00:00.2 UTC is equivalent to 30 November 2012 at 23:59:59.9. The rejected bidder claims "Greenwich mean time" means UT1, because that is the most widely used approximation to the true mean rotation of the earth. The winning bidder claims that "Greenwich mean time" means UTC, because in the absence of a clear legal definition, words have their ordinary day-to-day meaning, and most people, whether they know it or not, attempt to set their clocks to UTC (in the UK when summer time is not in effect). Which interpretation is correct? I don't know. --Gerry Ashton (talk) 15:11, 1 August 2008 (UTC)
The good people of the United Kingdom, without regard to what they attempt to set their clocks, are not in need of a clear legal definition of the time scale recognized in UK law; they have one! Tomorrow, 2 August, will begin the 129th year of Greenwich mean time being the legal time scale in the United Kingdom. It was on that date that Queen Victoria gave her assent to the following:

Whenever any expression of time occurs in any Acts of Parliament, deed, or other legal instrument, the time referred shall, unless it is otherwise specifically stated, be held in the case of Great Britain to be Greenwich mean time, and in the case of Ireland, Dublin mean time. Act 43 & 44 Vict. c.9

In 1880 Greenwich mean time, for civil but not astronomical uses, meant mean solar time at the Greenwich meridian with the hours and days reckoned from midnight. In the intervening 129 years, most of Ireland has abandoned the United Kingdom and the people of the United Kingdom have abandoned Greenwich mean time, but the law stubbornly has not. I direct you again to recent debate in the House of Lords. [2]
The supremacy of GMT over UTC may be unresolved in your mind, but it's not unresolved in law. As stupid as it may seem, the correct interpretation to your hypothetical is clearly that the intended time scale was GMT. Until Parliament sees fit to bring the UK's legally recognized time scale out of the 19th century and into the 20th (the 21st would be asking too much), we in the UK live UTC lives but are ruled by GMT laws. --Blake the bookbinder (talk) 19:57, 1 August 2008 (UTC)
The thing about the 1880 law (and subsequent laws, as far as I can tell) is that it does not specify who is to compute GMT nor what procedures are to be used. There is nothing to stop someone from keeping GMT by performing his own telescopic observations, independent of any government authority. Thus it is up to the courts, in any dispute, to decide which approximation to GMT should be used. (Every time measurement is an approximation). A court might very well decide that since the Greenwich Observatory sent telegraphic time signals throughout the country (and some points abroad) in 1880, those signals must have been the approximation to GMT that the parliament had in mind when it passed the 1880 law. The nearest analog to those signals today might be considered the time provided by the National Physical Laboratory through radio broadcasts, which are UTC(NPL). Thus a court might decide to treat UTC(NPL) as the most appropriate approximation to GMT in cases that do not specifically involve astronomy, science, or navigation (which are called out in some of the time laws). --Gerry Ashton (talk) 20:51, 1 August 2008 (UTC)
The Act of Settlement 1701 does not specify what procedures are to be used if Queen Victoria should ever be cloned (would she immediately regain the throne upon her [re]birth?, would she have to wait till the death of the present monarch?, would she regain her throne at all?) There is nothing to stop her from making a claim to the throne, independent of any regal authority. Thus it is up to the courts, in any dispute, to decide the position of cloned monarchs in the order of succession. A court might very well decide that since the monarch has always been the living descendant of the Electress Sophia of Hanover with the highest rank in the order of succession (and who is not a Roman Catholic, or married to one), that that is what the framers had in mind when they passed the 1701 Act. In an age of cloning, the nearest analogue to the highest-ranking living descendant of Electress Sophia might be considered the result of cloning the cells of a lock of Victoria’s hair. Thus a court might decide to treat Victoria (v. 2.0) as the most appropriate person to reign over the United Kingdom (in cases that do not specifically involve non-GM monarchs).
A bit of Sunday morning whimsy, but at least it’s a situation that needs, or will one day, a judicial decision (as opposed to the legality of GMT in the UK, which is a settled issue).
Gerry, your argument that the legal standing of Greenwich mean time is in dispute might have something in it if the UK had only recently begun to use UTC in public life, but the very fact that UTC has been in use for over 36 years, that in those 36 years laws and regulations have continued to be promulgated using the term “Greenwich mean time” while UTC was the de facto time scale, and that on at least one occasion the government of the day intentionally declined to act on a proposed bill to change the legal time scale from Greenwich mean time to Coordinated Universal Time (a bill that had the support of the Astronomer Royal, no less) proves to me, and to any court, that Greenwich mean time is what the law has meant by “Greenwich mean time” every day since August 2, 1880 up to, and including, today. If you are considering submitting a bid or making large, important bank payments in the future, I wouldn’t wait till the last half second of the day to do it: Ignorance of the law is no defense.--Blake the bookbinder (talk) 10:23, 3 August 2008 (UTC)
Blake, I do not argue that the legal status of Greenwich Mean Time is in dispute, I argue that no national time dissemination service, either in the UK or elsewhere, makes any time scale available named "Greenwich Mean Time". So Blake, let me ask two questions. (1) If you wanted to time an event in near-real-time with an accuracy of 0.1 s in GMT, and you had all the precision equipment you wanted, what available time scale would you use, and what if any modifications would you make to the time scale? (2) Same question, except you have 2 months to decide what the time of the event was? --Gerry Ashton (talk) 15:42, 3 August 2008 (UTC)
Gerry, now we’re getting somewhere! We’re in agreement that the legal time scale (the one recognised by law in the UK) is GMT, and that no national time dissemination service, in the UK or elsewhere (so far as I know), disseminates GMT. Breaking things down to basic assumptions might be the way to go; let me run a few by you and you can reply agree, disagree or don’t know (with explanation if you want). I believe all of these to be true.
"Civil time" is the time scale used by the general public in daily life.
In the UK, civil time is the time disseminated by the National Physical Laboratory.
The time disseminated by the National Physical Laboratory is UTC.
In the UK, civil time is UTC.
In the UK, legal time ought to be UTC.
The definition of UTC is not the same as the definition of GMT and when UTC and GMT are the same, it’s coincidental.
About the two questions you’ve posed; I haven’t got a clue! I don’t know what exactly you want to elicit from me so I don’t really know how to approach them. If I wanted to determine what time an event happened on the GMT time scale I’d hire a team of competent blokes and have them figure it out and staple the answer to their invoice for the job. I believe that the GMT time scale is too elastic and/or irregular to be of use in a world built for precision. I doubt GMT is appropriate for events that need to be measured to the tenth of a second, or better. I don’t know what the second question is fishing for, unless it’s to point out that a GMT day, two months after the event, will likely be of a different length than the day of the event. If there’s some other bit of the whole scenario you want me to opine about, I’ll try, but you’ll have to ask me in a different way, that is, point blank.
If we can tackle more than one thing at a time, how about steering this discussion back to the subject of your sandbox draft of the opening paragraphs of the UTC article.? I’ll just throw out a few questions, that are not necessarily things I’d change – just some points around which to start a conversation about something that may pay dividends.
I know it’s been there for a long time, but why does this article give the French translation of Coordinated Universal Time? The header for the GMT article is not followed by (Fr. Temps moyen de Greenwich). I’m sure every article title has a French translation, but we don’t usually include it.
In the sentence fragment, “…is one of several replacements for Greenwich Mean Time, which was mean solar time at the Royal Observatory, Greenwich, England” why do you define Greenwich mean time when a simple click on the link would take the reader to a complete definition; the beauty of Wikipedia is that terms and definitions are linked like that.
The article mentions UTC replacing GMT then another replacement called UT1 and then follows with a sentence that starts, “This replacement became necessary…” To which replacement is “[t]his replacement” referring?
And just one more to chew on tonight: Should the opening paragraph try to give the history of UTC, or define it? Your draft mentions GMT and the Royal Observatory and UT1 and the 1930s and unsteady rotation and 1956 and 1961 and gets through all that without ever telling me what UTC is. Wouldn’t a definition be appropriate here? I know there are many who want GMT in the opening paragraph (I think they’d be happy if it said “Don’t worry, UTC is just French for GMT!”) but can we not define UTC at the top of the article and save GMT for the third paragraph, or wherever history is covered? I don’t want to obscure UTC’s relationship to GMT, but UTC is not GMT and the definition of UTC is not “the replacement for GMT”. Gordon Brown’s Wikipedia article doesn’t start with “Gordon Brown (Fr. Gordón Marron) is the replacement for Tony Blair.”
OK, I’m done. I really do enjoy these “conversations”, even though they are so easy to misunderstand. I have so little need to write in my work life; it’s good to have somebody to spar with in a friendly and creative atmosphere. (How about replying to this post at the bottom of the page and outdented all the way to the left? We're going to run out of room over here on the right!) --Blake the bookbinder (talk) 21:44, 3 August 2008 (UTC)


What this article needs is a short introduction that everyone can understand. I would say the first paragraph could read something like this after combining what we have said:
Coordinated Universal Time is the standard time scale which is the basis of civil time across the world. UTC is used internationally so that it is the same everywhere regardless of local time zones. UTC developed initially from Greenwich Mean Time (GMT) and with increasing demand for accurate timekeeping, this new time scale was created by adding leap seconds to International Atomic Time (TAI) to compensate for the Earth's slowing rotation. This is now known as UTC and closely follows GMT, which is recognised as UT1 internationally
I hope that's better, admittedly some might need a bit of reworking, especially the "same everywhere" part.--AlexTheComposer (talk) 07:41, 1 August 2008 (UTC)

I've been thinking that GMT and the various Universal Times are really different animals. Let me try to put them into categories:
Conceptual time scale: GMT
Measured time scale, available retrospectively: UT0(xxx), UT1, UTC
Measured time scale, available near-real-time: UTC(NIST), UTC(NPL), UTC(USNO), etc.

Obviously the time scales available near-real-time are the easiest to use in day-to-day affairs. --Gerry Ashton (talk) 21:25, 1 August 2008 (UTC)

I have added some of the information from this discussion as a footnote in my sandbox. --Gerry Ashton (talk) 16:27, 2 August 2008 (UTC)

Meaning/realization of GMT

In the previous section, Blake the Bookbinder asked for responses to a number of points or questions. The previous section had too may levels of indention, and was getting to long, so I'm answering here. Except this paragraph, unindented text is from Blake.

Gerry, now we're getting somewhere! We're in agreement that the legal time scale (the one recognised by law in the UK) is GMT, and that no national time dissemination service, in the UK or elsewhere (so far as I know), disseminates GMT. Breaking things down to basic assumptions might be the way to go; let me run a few by you and you can reply agree, disagree or don't know (with explanation if you want). I believe all of these to be true.

"Civil time" is the time scale used by the general public in daily life.

That's one meaning, but it might mean legal time too.

In the UK, civil time is the time disseminated by the National Physical Laboratory.

The time in everyday use is disseminated by NPL, but depending on dissemination mode, there may or may not be a summer time indicator.

The time disseminated by the National Physical Laboratory is UTC.

The time disseminated for real-time use by NPL is UTC(NPL).

In the UK, civil time is UTC.

The everyday time in the UK is either UTC(NPL) or the correspoinding summer time.

In the UK, legal time ought to be UTC.

Pro
  • When GMT was defined in 1880 as legal time, it was widely available to the public through telegraph signals. UTC(NPL) is the corresponding widely available time.
  • All countries that have explicitly chosen a UT variant for their legal time have chosen UTC; if the UK does too it will follow in the same tradition of international cooperation that lead to the prime meredian running through Greenwich.
Con
  • It is too presumptious to change the number of seconds in some minutes without an act of Parliament. Many devices and computers cannot accommodate this change.

The definition of UTC is not the same as the definition of GMT and when UTC and GMT are the same, it's coincidental.

Undecided.

About the two questions you've posed; I haven't got a clue! I don't know what exactly you want to elicit from me so I don't really know how to approach them. If I wanted to determine what time an event happened on the GMT time scale I'd hire a team of competent blokes and have them figure it out and staple the answer to their invoice for the job. I believe that the GMT time scale is too elastic and/or irregular to be of use in a world built for precision. I doubt GMT is appropriate for events that need to be measured to the tenth of a second, or better. I don't know what the second question is fishing for, unless it's to point out that a GMT day, two months after the event, will likely be of a different length than the day of the event. If there's some other bit of the whole scenario you want me to opine about, I'll try, but you'll have to ask me in a different way, that is, point blank.

I'll give my answers. My best guess is that in case of a dispute, a court would decide that UTC is the most appropriate approximation to use for GMT when legal time is required. Therefore if I needed to time an event to an accuracy of 0.1 s, I would use UTC(NPL). If someone else decided UT1 was the right answer, that person should use the best real-time approximation or prediction of UT1 he/she can find. If the result isn't needed immediately, the person should record it in UTC(NPL) and apply corrections when they are announced about a week later. The corrections are negligible between UTC(NPL) and UTC.

If we can tackle more than one thing at a time, how about steering this discussion back to the subject of your sandbox draft of the opening paragraphs of the UTC article.? I'll just throw out a few questions, that are not necessarily things I'd change – just some points around which to start a conversation about something that may pay dividends.

I know it's been there for a long time, but why does this article give the French translation of Coordinated Universal Time? The header for the GMT article is not followed by (Fr. Temps moyen de Greenwich). I'm sure every article title has a French translation, but we don't usually include it.

I thought about deleting that.

In the sentence fragment, “…is one of several replacements for Greenwich Mean Time, which was mean solar time at the Royal Observatory, Greenwich, England” why do you define Greenwich mean time when a simple click on the link would take the reader to a complete definition; the beauty of Wikipedia is that terms and definitions are linked like that.

That article could change from time to time; even if I thought it did the job today, it might not in the future.

The article mentions UTC replacing GMT then another replacement called UT1 and then follows with a sentence that starts, “This replacement became necessary…” To which replacement is “[t]his replacement” referring?

It refers to Universal Time in general; that could probably be phrased better.

And just one more to chew on tonight: Should the opening paragraph try to give the history of UTC, or define it? Your draft mentions GMT and the Royal Observatory and UT1 and the 1930s and unsteady rotation and 1956 and 1961 and gets through all that without ever telling me what UTC is. Wouldn't a definition be appropriate here? I know there are many who want GMT in the opening paragraph (I think they'd be happy if it said “Don't worry, UTC is just French for GMT!”) but can we not define UTC at the top of the article and save GMT for the third paragraph, or wherever history is covered? I don't want to obscure UTC's relationship to GMT, but UTC is not GMT and the definition of UTC is not "the replacement for GMT”. Gordon Brown's Wikipedia article doesn't start with “Gordon Brown (Fr. Gordón Marron) is the replacement for Tony Blair."

All we can do is describe it really. We can either describe it by who produces it (BIPM), or with a historical description. A real definition would probably fill a bookshelf.

--Gerry Ashton (talk) 03:40, 4 August 2008 (UTC)

Gerry, what's your definition of Civil Time?--Blake the bookbinder (talk) 17:41, 4 August 2008 (UTC)

I won't use the term "Civil Time" myself because it is too ambiguous. It might be the time the proverbial "man on the street" tries to keep his watch synchronized to, or it might be the time legally in effect in a certain location. If someone else uses it, I'd try to figure out the meaning from context. --Gerry Ashton (talk) 17:46, 4 August 2008 (UTC)

Proposed change to intro

User:WikieWikieWikie changed the introduction to read as follows:

Coordinated Universal Time (French Temps Universel Coordonné), or UTC, is the international time standard kept by the observance of International Atomic Time (TAI), with additions of leap seconds at irregular intervals to compensate for the slowing of the Earth's rotation. The mean solar time at the Royal Observatory, Greenwich, known as GMT, was a form of Universal Time we know as UT0, and the first international standard for time. With polar motion of the Earth in consideration, though, UT0 was, and is not truly universal time, and the observations at Greenwich were, and are not capaple of accurate UT measurements. UT1, is now in use with computations of the Earth's current position. It is on the basis of the UT1 computations, and the calculation of the Earth's slowing rotation, UTC serves as our international standard time.

I don't think this change is helpful for several reasons, and have reverted the change. For one thing, it is confusing to say what is or is not "universal"; our current phrase "universal time" ignores locations other than earth in the universe. It is confusing to say that observations at Greenwich were not accurate measurements; without a source to the contrary, I would expect that the measurements were considered accurate for their time. Also, the sentence "it is on the basis of the UT1 computations, and the calculation of the Earth's slowing rotation, UTC serves as our international standard time" is long, confusing, and emphasizes only calculation with no mention of measurement, and adds to the confusion with the phrase "standard time", which is usually used to mean zone time with no daylight savings adjustment. --Gerry Ashton (talk) 02:37, 8 August 2008 (UTC)

What kind of writing uses UTC?

On 10 August User:Abberley2 changed a sentence in the intro to read "In casual informal use, Greenwich Mean Time (GMT) is the same as UTC and UT1. Owing to the ambiguity of whether UTC or UT1 is meant, and because timekeeping laws usually refer to UTC, GMT is avoided in careful technical writing."

I don't think there is a problem with the change of "casual" to "informal", but I'm concerned about changing "careful" to "technical". I don't think it's right to imply that informal and non-technical go together, and that formal and technical go together. The changed wording would suggest that UTC should be avoided unless sub-second precision is necessary, or the in scientific and high-technology use. --Gerry Ashton (talk) 00:51, 11 August 2008 (UTC)

You can write a paragraph that uses "GMT" a dozen times and it can be both technical and carefully written. What should be avoided is giving so much attention to GMT in the opening of an article about UTC. --Blake the bookbinder (talk) 18:08, 12 August 2008 (UTC)

81.98.162.220's question

The editor using IP address 81.98.162.220 added a {{fact}} tag and used this edit summary:

(PLZ READ DONT JUST ADD REF! If it has been changed to track UT1 it can not now be approximating UT1 with the correction!!! ONE OF THESE THINGS IS WRONG.)

I don't quite understand the edit summary. I'll explain how I understand it, and perhaps the editor will follow up with questions.

Before 1972 the length of the UTC second was changed slightly to make UTC be an approximation of UT2. Beginning 1972, two changes were made. First, the goal was to approximate UT1, not UT2. Second, the second was always the SI second provided by atomic clocks, and leap seconds were used to keep UTC within 0.5 s of UT1 (later this was relaxed to 0.9 s). So UTC used to be an approximation to UT2, and now it is an approximation to UT1. --Gerry Ashton (talk) 15:17, 19 October 2008 (UTC)

I think the anonymous editor is contrasting "tracking" with "approximating". He probably thinks that if you track something, you are much closer to its true value than merely approximating it. But there are different degrees of "tracking" and "approximating". The 1962–1971 version of UTC tracked UT1 much closer than the post-1971 version did. The IERS provides a graph covering this entire range which shows small deviations of +100 ms to −160 ms between 1962 and 1971, but large deviations of +780 ms to −670 ms from 1972 to 2008. Before 1960, the time signals broadcast by several countries were received at different times on a shortwave radio. Coordination of broadcast time began 1 January 1960 via the cooperation of the US and UK, entrusted to BIH in 1961, and formalized by CCIR (now ITU-R) in 1963. The allowable deviation of UTC from UT2 was ±100 ms from 1963 to 1971. The allowable deviation of UTC from UT1 of ±700 ms between 1972 and 1974 was immediately violated in 1973 with a +760 ms deviation, so the limit was relaxed to ±900 ms after 1974. See "The leap second: its history and possible future". For the graph, go to the IERS website and select "EOP series: analysis" from the list on the left, accessing the page "Analysis of the Earth Orientation Parameters". Type "1960" in "Begin", click on the radio button below "UT1–UTC" in the "Select EOP" row (the default "Comb. C01" is OK), then click on the "Submit" button beneath the list. — Joe Kress (talk) 21:14, 19 October 2008 (UTC)

Coordinate time.

Should the article state that UTC is a coordinate time, as opposed to proper time? Clock are now becoming more and more accurate that this distinction is becoming more important. Martin Hogbin (talk) 17:45, 26 October 2008 (UTC)

I wonder if that topic would be better covered in International Atomic Time. By the way, I believe the word "coordinated" in "Coordinated Universal Time" has nothing to do with coordinate time vs. proper time. Rather, it refers to the fact that in the early days of atomic clocks and radio time signals, each national time laboratory broadcast time signals as it saw fit. Later they cooperated, and made the various national radio time signals as nearly synchronous as the technology allowed. That is, they coordinated their time signals. --Gerry Ashton (talk) 18:36, 26 October 2008 (UTC)
I was not suggesting any connection between the 'coordinated' and coordinate time. Martin Hogbin (talk) 19:20, 26 October 2008 (UTC)
Archive 1Archive 2Archive 3
  1. ^ AOPA Aviation Time. AOPA's PATH to Aviation. Accessed 2007-02-25.
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