Wikipedia:Reference desk/Archives/Science/2008 January 27

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January 27

Summer Solstice

In the eleventh century what was the date for the summer solstice? Is it correct that the summer solstice swings between the dates of June 20 and June 24 over thousands of year? When (century) was the summer solstice June 24 (Midsummer's Day)? --Doug ^talk 00:15, 27 January 2008 (UTC)

see this calculator. Remember to convert the Gregorian result to a Julian date. - Nunh-huh 02:12, 27 January 2008 (UTC)

Cross breeding of rats and squirrels

Is it possible for rats and squirrels to crossbreed? I know they are different species, but there are cases of different species breeding (the mule being the most obvious). Also, in general, what are the requirements for species being able to interbreed? --Evan Seeds (talk)(contrib.) 03:28, 27 January 2008 (UTC)

The more closely the species are related, the more likelihood of success. If the species have recently diverged, it's more likely that they have a similar number of chromosomes, and it's more likely that their offspring won't suffer from a fatal lack (or surfeit) of genetic material. Horses have 32 pairs of chromosomes, while donkeys have 31 pairs, and the species have recently diverged: they both belong to the same genus. Rats have 20 pairs of chromosomes, while squirrels have 27 pairs, and have diverged far more: they both belong to the same order (Rodentia), but different families as well as different genuses. - Nunh-huh 03:43, 27 January 2008 (UTC)

Furthermore, even within the family Muridae the diversity is astonishing. Quoting from Nakamura et.al. :

the diploid chromosome numbers (of Muridae) range from 2n = 10 in Akodon species ... to 2n = 102 in Tympanoctomys barrerae.

Cheers, Dr_Dima. —Preceding comment was added at 15:53, 27 January 2008 (UTC)

I don't think that's too surprising. Rodents were the first mammals to evolve and have relatively short lives and breed a lot. As a consequence you'd expect a lot more evolutionary diversity there than in horses and the like, which are relatively recent and live relatively long lives. --24.147.69.31 (talk) 03:28, 28 January 2008 (UTC)

Strictly speaking, "Rodents were the first mammals to evolve" is nonsense: all mammals are equally descended from "the first mammals to evolve". I assume .31 means that the first mammals resemble today's rodents more than they resemble other orders. —Tamfang (talk) 23:16, 28 January 2008 (UTC)

Medical one way material

Im looking for the corrct english name for "medical one way material" (german: medizinisches Einwegmaterial). For instance most Scalpels, plastic stuff or medical syringes are made for one-way use only. I want to create this category in Commons. Is there an english article in Wikipedia about "medical one way material"? --84.137.47.124 (talk) 13:55, 27 January 2008 (UTC)

Probably "single use item" or "disposable item". -- Finlay McWalter | Talk 14:09, 27 January 2008 (UTC)

I think "disposable medical products" will do best. (most google-hits) Thanks! --84.137.47.124 (talk) 15:05, 27 January 2008 (UTC)

I think "single-use item" (with a hyphen, please) is much better. It conveys the fact that you aren't intended to use it more than once. An item that you use a few times and then discard, like a razor blade, is also "disposable". --Anonymous, 23:47 UTC, January 27, 2008.

Inhaler dream

Last night (in a dream) I was standing around in the ocean maybe 100 yards out (it was shallow) with friends I've never seen before. We had a gigantic inflatable raft that everyone was sitting on in deck chairs. One guy had asthma and kept coughing and using his inhaler. Someone splashed him from the water and his inhaler got a little wet. It started hissing a little.. he shrugged, capped it, and put it back in his pocket, then we all went in the water. The inhaler got totally wet and he pulled it out to use it I guess but foam was now pouring out of it. I shouted nooooooooo and dove for it in slow motion, grabbed it, and reached back to throw it, but someone grabbed my wrist and said hey dude not cool give it back to him. I shook off his hand and managed to toss it but he batted my hand and it only went a few yards. The asthmatic guy realized what was going on and dove in slow motion between me and where the inhaler hit the water. As soon as he came between me and it, there was a deep thump in the water and I could feel feet of water rushing past my legs. His eyes crossed in pain and an instant later, a mountain of boiling steam erupted from the ocean behind him. It was a few yards across and a lot higher than wide. He was blown forward and landed right in front of me, then I woke up. How much volume of gas is actually in one of these inhalers?! -froth —Preceding unsigned comment added by Froth (talk • contribs) 16:09, 27 January 2008 (UTC)

Metered dose inhalers usually contain a small amount of medication dissolved in a haloalkane. When full, the canister is completely filled with liquid haloalkane, and thus the volume of gas in the inhaler is about zero. When the inhaler is depleted, it will be filled with the haloalkane gas (at a much lower pressure) or air (depending on the valve mechanism), with a volume equal to the volume of the space in the inhaler bottle, I would guess around 25cc. Hopefully someone will come along shortly and be able to tell you the volume of gas at atmospheric pressure which is created from the volume of liquid in an inhaler, as that is probably what you are looking for, but until then, the answer to your question as stated would be somewhere between zero and the volume of the canister. Tuckerekcut (talk) 18:15, 27 January 2008 (UTC)

So no real explosive potential or catastrophic reactions with salt water? --f f r o t h 18:27, 27 January 2008 (UTC)

Well, Trifluoromonofluoroethane and Heptafluoropropane, two propellants used in inhalers, have vapor pressures of 70 and 44 psig, respectively, at room temperature. So a tiny amount of gas will build up inside the container until this pressure is reached. Suffice it to say I wouldn't want to puncture an aluminum can at 70psi anywhere near my face, but such a small volume of gas, and such a small mass of possible shrapnel is unlikely to do impressive damage, in my unproven and nearly anonymous opinion. Tuckerekcut (talk) 19:07, 27 January 2008 (UTC)

(Returning to a theme of a few weeks ago), in the process of "safing" inhalers so that I could recycle the aluminum canisters, I've punctured them with an automatic center punch; nothing exciting happens. (And yes, they still contained some of the propellant in liquid form so they were still in equilibrium at full pressure.) The canisters appear to be quite strong compared to the pressure involved, so a small puncture doesn't cause a catastrophic "tear-out" of the can.

Atlant (talk) 21:06, 27 January 2008 (UTC)

Once I managed to get an inhaler into the clothes dryer. The heat caused the gas to build up enough pressure to push the concave bottom of the canister into a convex bulge, so they aren't completely invincible. HYENASTE 03:11, 28 January 2008 (UTC)

Ideal tax rate

Obviously, it can't be 100% as no money would be left for private industry, and obviously it can't be 0% as that would leave no money for public education, roads, airports, seaports, fire departments, police departments, etc.; thus providing no infrastructure for a growing economy. My question, then, is what is the ideal tax rate for maximum growth of the economy ? I realize this is a very difficult question to answer. I would expect that a chart correlating various net tax rates and long term growth rates in countries around the world could go a long way toward answering this question. Perhaps the net tax rate could be found by dividing the total of all taxes collected by national, provincial, and local governments in a country for a year by the annual national product. Do we have any such chart ? StuRat (talk) 17:28, 27 January 2008 (UTC)

Wouldn't the ideal rate depend on your personal or your nation's economic philosophy? Probably the lower it is, the higher the growth rate; the problem is (as you pointed out} providing public goods with a very low tax rate. Some of these things could theoretically be provided privately. I don't see why airports and seaports, for example, couldn't be owned and run by airlines/shipping lines (or a group of airlines/shipping lins owning shares). (It would probably raise prices, though...) Vultur (talk) 18:17, 27 January 2008 (UTC)

It definitely depends on the economic philosophy. As a libertarian, I think taxes should be as low as possible, and that most of the things on your list shouldn't be run by the government. Education should be privatized, and roads should be privately owned and maintained, as well as airports and seaports. (I also disagree with Vultur's prediction that this would raise prices. Competition in the market usually decreases prices in the long run.)

Also, I disagree with your (StuRat's) unquestioned use of "growth of the economy" as a figure of merit. A nation shouldn't be judged by its total size or wealth, but by the freedoms and quality of life enjoyed by its citizens. Growth isn't always good. (See VHEMT for another example of this philosophy that may surprising you.) Just some things to think about... —Keenan Pepper 19:16, 27 January 2008 (UTC)

I can't agree that lower tax rates are always better, which means 0% is ideal. That means no public education, which inevitably results in large portions of the population being ignorant and condemned to lives of poverty. This isn't just bad for them, it's bad for the economy of the country as well. StuRat (talk) 03:41, 28 January 2008 (UTC)

Tocqueville commented on the high degree of literacy, and appetite for books, among Americans a generation before the movement for public schooling (which is not the same thing as education) really got going. We might also observe the large portions of the population who are ignorant and condemned to poverty with public schooling. Like almost everything else on your list, education was done privately long before government stepped in and told us that it can't be done privately. —Tamfang (talk) 23:13, 28 January 2008 (UTC)

I believe that literacy rates are considerably higher in nations with compulsory public education than those without: See List of countries by literacy rate. Interestingly, communist and former communist countries score quite well on literacy, since, despite it's many other shortcomings, communism does promote compulsory public education (with the occasional exception, like Cambodia under the Khmer Rouge). Even poor nations, like Albania, manage a high rate of literacy due to compulsory public education. And, despite Tocqueville's comments, I believe US literacy rates were much lower at the time than now: [1]. Black illiteracy rates were around 80% in 1870 and dropped to under 2% by 1979, for example. StuRat (talk) 04:39, 29 January 2008 (UTC)

Wasn't it a crime to teach slaves to read? —Tamfang (talk) 16:34, 1 February 2008 (UTC)

0% works pretty well in Snow Crash and roads still get built and children still go to school --f f r o t h 19:55, 27 January 2008 (UTC)

Yes: Laffer curve. The details, e.g., progressivity and the needs of government such as war or a retiring population -- seem to be much more important than the average rate. MilesAgain (talk) 20:06, 27 January 2008 (UTC)

That seems to be the correct article, thanks. However, they only talk about it in theory, no actual numbers are provided. Certainly somebody could come up with some approximation of the ideal tax rate (10% or 90% ?). StuRat (talk) 03:41, 28 January 2008 (UTC)

Over at Laffer curve I found an excellent summary of any discussion on an ideal tas rate: here. --Ouro (blah blah) 14:55, 28 January 2008 (UTC)

Exactly; as I said, the percentage number is not as important as the other factors determining the ideal rate. Under some conditions, 1% may be ideal, but under others, 50% could be best. 20% could be good under progressive tax tables, but bad under a flat tax, all other things being equal. MilesAgain (talk) 19:32, 28 January 2008 (UTC)

The thing is, not all nations even collect tax. Some of the small oil-rich countries in the Middle East, for example, have the lowest tax rate in the world (if you mean tax the way I'm percieving it), and in fact give a reverse-tax system. I'm not sure of the details, though. Hope this helps. Thanks. ~AH1^(TCU) 19:43, 1 February 2008 (UTC)

Mesozoic bird taxonomy

I'm having trouble finding out what family, if any, Paraprotopteryx is in. I'm working on the article for this genus now. It appears to be incertae sedis, but can someone confirm this? Vultur (talk) 18:18, 27 January 2008 (UTC)

Not much on google, is there? Found a wiki confirmation here[2] in the section Avian incertae sedis in the List of fossil birds. Julia Rossi (talk) 03:52, 28 January 2008 (UTC)

Fossils from mountains and islands

Sorry to ask two paleontology questions in succession, but is it true that mountains and small islands such as atolls have left no fossils, so we don't know what the Mesozoic mountain species were? Vultur (talk) 18:20, 27 January 2008 (UTC) —Preceding unsigned comment added by Vultur (talk • contribs) 18:19, 27 January 2008 (UTC)

Think about where there could have been rocks formed on a mountain. Most rocks are formed in hollows like lakes, rivers, oceans. Perhaps there are some fossils preserved under volcanic lava flows. Recent atolls are likely to have coral fossils, but mountain species are not likely to live on an atoll. Graeme Bartlett (talk) 21:20, 27 January 2008 (UTC)

Sorry, the atolls were a separate question. I read a book called "Life: The First Four Billion Years" where the author said that any islands in Panthalassa, when Pangaea was around, left no fossils or rocks at all - anything could have been there. I was asking how accurate that was. 98.199.17.94 (talk) 22:55, 27 January 2008 (UTC)

Isolated atolls on the ocean floor move around on the oceanic plate. Ususally oceanic crust is swallowed up in a subduction zone in a oceanic trench. This is broought down to great depths and usually melted to form magma. Fossils do not survive this treatement. It is possible for seamountains to be accreated to the side of a continental margin. But I don't know if any have done this from the Mesozoic or not. And if they did whether there were fossils. Graeme Bartlett (talk) 23:12, 27 January 2008 (UTC)

Also, just because there are mountains today doesn't nessecarily mean that they were there in the mesozoic era. The Rockies and Andes were just starting to come up, and some, like the Alps and Himalayas, weren't created until recently. The Himalayas, containing some of the tallest mountains on Earth, for exapmle, was created when India collided into Asia, which happened around 50 million years ago, after the mesozoic era. However, continents moving against oceanic plates can produce mountains and plateaus, as well as volcanoes. The Rockies and Andes are not moving against land, but rather the Pacific ocean, and the Deccan Traps have been around since the Cretaceous. Hope this helps. Thanks. ~AH1^(TCU) 19:39, 1 February 2008 (UTC)

Big flashes of flame while cooking

When people are cooking something in a pan, probably mixing it around everything, and they make those big flashes of flame, what's going on? Where is the flame coming from? What's the purpose and how do I copy it? Does it have a name? ----Seans Potato Business 18:29, 27 January 2008 (UTC)

I think you mean Flambé. Hope this helps. --Dr Dima (talk) 18:40, 27 January 2008 (UTC)

In general add a liquid containing alot of alcohol and let the alcohol boil of - it then ignites - you need a gas stove to do this (or a match)

The alternative is flashes from very hot oil - such as can be obtained when stir frying - it's the same sort of thing - oil vapour is igniting - it needs to be very hot - and sometimes a lid is needed to put the fire out..77.86.108.68 (talk) 18:54, 27 January 2008 (UTC)

If Sean is thinking of stir frying, as in Chinese and Thai cooking, the flashes are definitely burning oil, not alcohol (i.e. not flambé). Alcohol (in cooking, at least) generally burns blue, slowly, and relatively cool, while oil flashing to vapor and burning is generally more yellow, quick, and hot. Also, flambé is a very deliberate, show-off technique, which is rarely done in the kitchen, rather right at the table in front of the consumer. (If you're going to add an expensive liqueur to a dish and then burn most of it right back off, you don't want to waste the effect, since the effect is all there is.) —Steve Summit (talk) 19:30, 27 January 2008 (UTC)

I'm thinking of the Chinese/Thai oil stuff. --Seans Potato Business 19:36, 27 January 2008 (UTC)

Get the oil very hot - then move the pan about like you are a proper chef maybe tilt it a bit - you really need gas - hopefully the oil will ignite.. if the oil is really hot so that it's spitting you may burn your eyebrows off etc. As I said before having a lid ready to put it out is a good idea. Also as far as I know it's not intentional and doesn't really add the the taste - just a hazard involved with cooking with very hot oil..83.100.183.193 (talk) 20:53, 27 January 2008 (UTC)

Southern Chinese cuisine often DO put rice wine (rich in alcohol) in stir-fries to aid the flame. --antilived^{T | C | G} 00:24, 30 January 2008 (UTC)

Flambé isn't just for show. Cooking that uses alcoholic beverages for deglazing the pan will often end with the flaring-off of the alcohol portion and the ignition is usually deliberate.

Atlant (talk) 21:11, 27 January 2008 (UTC)

It is relatively easy, using a flat cast-iron griddle on a gas stove, to get the oil hot enough that vapor forms, and then to ignite it at the edge of the pan with the stove flame. This is less common on electric ranges (no flame underneath). This would cause a grease fire across the entire pan; the stir frying method keeps things moving so that you only get flashes.

Flambe is similar in that there is a vapor that ignites, but the alcohol burns at a relatively low temperature and is quickly consumed. A large amount of oil in a pot, however, might continue to vaporize during burning, like a candle, such that the grease fire is fed continuously.

Turning the stove off would lessen the temperature of the oil, perhaps killing the supply of vapor. Covering with a damp cloth or lid would cut off the oxygen supply to similar effect. Throwing water on the fire would produce a bolus of steam directly under the flaming vapor, launching a fireball skyward with great destructive effect. Not advisable. Bckirkup (talk) 23:39, 2 February 2008 (UTC)

Danger of collecting blood samples for experiment

In such a case where one is collecting blood samples from the general population, there is surely a risk (to all parties concerned but I'm not addressing that right now) to the person collecting blood. Why then is not justified that they wear a mouthmask and safety glasses to protect their mucosal surfaces? How small is the risk? ----Seans Potato Business 19:34, 27 January 2008 (UTC)

As long as the vials of blood remain intact, there's no way for blood to get from the patient onto the mucosal surfaces of the phlebotomist. During the blood draw, blood is contained by the steel needle and then in the glass vials. In principle, it would be possible for a small amount of blood to be aerosolized if a vial were dropped and smashed, and for a small amount of that aerosol to settle on the mucosa of the phlebotomist. Similar aerosolization could occur if the phlebotomist were to fling blood-contaminated equipment about in the air. (The latter is an unlikely thing to have happen, and suggests a neglect of other basic safety precautions....)

Note that unless the blood is agitated to generate pathogen-laden aerosols, there is no risk from standing blood or blood droplets. (Clinicians and experimenters who handle pathogenic materials are – or ought to be – trained in techniques that minimize aerosol creation during the course of their tests.) Viruses, bacteria, and parasites won't evaporate, and won't travel through the air without help. Only small, non-infectious molecules (mostly water) will enter the air spontaneously by evaporation.

In short, aerosolization of blood during phlebotomy is very rare in the first place, and even where it does occur only small amounts of blood (and and correspondingly small load of pathogens) will be aerosolized. Of that pathogenic aerosolized material, only a vanishingly small fraction is likely to settle on a phlebotomist's mucosa. Many blood-borne pathogens – including many of the nasty ones like HIV and hepatitis C – are very ineffective at infection across healthy mucosa. Finally, in drawing blood from a general (superficially healthy) population for research purposes, the likelihood of the blood carrying any serious disease is quite small. The cost, inconvenience, and/or discomfort of masks and glasses aren't generally seen as a worthwhile tradeoff to defend against an extraordinarily tiny risk. Greater precautions may be taken in drawing blood from patients with known serious diseases or serious and unexplained symptoms. TenOfAllTrades(talk) 20:46, 27 January 2008 (UTC)

Okay, thanks for that explanation; but what about gloves and does it matter what material the gloves are made from? Are some more resistant to puncture than others? --Seans Potato Business 21:33, 27 January 2008 (UTC)

Generally the flimsy gloves used by clinicians aren't going to make a whit of difference if they're handling sharps incorrectly. Needles and broken glass are sharp; they'll easily go right through both nitrile and latex gloves. Individuals who work with biohazardous sharps are (or should be) trained in proper handling techniques. (Never recap needles; don't pick up broken glass with your hands; etc.) Intact gloves (nitrile and latex are the most common types) are all quite adequate for protecting individuals from bodily fluids. Different brands of gloves will have modest differences in stretchiness, comfort, fit, and durability. TenOfAllTrades(talk) 17:45, 28 January 2008 (UTC)

When I was a young 'un, I used to work in a lab that tested people for cystic fibrosis and one of my jobs was to collect the blood samples each day from the doctors and extract the DNA from it. I used to wear gloves, a lab coat and safety glasses, but no mouth mask. Only on one occasion did the blood aerosolize, and that was when I managed to accidentally launch a vial across the lab, smashing it and spraying three of us with blood. That was not a good day. Twice I had to extract DNA from blood from known HIV positive people (that was real bad luck, I thought, having HIV and cystic fibrosis) and I sure as hell concentrated on good safety technique those days. As a totally irrelevant aside, I also had to extract DNA from mouthwash/cheek swabs and we found that people who had eaten an apple just before almost always gave crappy DNA samples. We guessed it was something to do with the acid. I learned two important things from that job: make sure your blood vials are clipped firmly to the rotator, and don't eat an apple before a buccal swab. Good times. Rockpocket 08:02, 29 January 2008 (UTC)

My lab supervisor has had 1ml LN2 stored vials containing various pathogens explode in her hand (well, maybe not explode, but burst open and spray their miniscule contents about). She's always careful to hold them such that only her glove (and the water bath she's thawing it in) get hit should a vial explode. To my knowledge, she's never gotten infected...Though maybe that's considered cheating. Cells tend to be fairly pissy after coming out of the deep freeze. Someguy1221 (talk) 08:16, 29 January 2008 (UTC)

Glaciers

Are glaciers geological features? You might think this is for homework, but no. I did a science mind map two months ago and never figured out this question. Please reply. I would greatly appriecate it. 99.248.42.43 (talk) 20:19, 27 January 2008 (UTC)

The answer probably depends on your definitions. Most people would agree that a geologic feature needs a degree of permanence to it. Glaciers tend to stick around quite a while by human standards, but ice ages bear testament to the mutability of glaciers. Additionally, the current state of widespread glacier retreat may impact your decision. — Lomn 20:29, 27 January 2008 (UTC)

However, the Morraines left behind by glaciers are most definitely a feature of the geological record. SpinningSpark 23:50, 27 January 2008 (UTC)

If "geological feature" means something that people in the field of Geology study, then sure -- glaciers are definitely studied by geologists. But then glaciers are also studied by people in other fields, like Climatology, so maybe they are "climatological features"? Then again, Glaciology is the study of glaciers, which would make glaciers "glaciological features". Maybe the nature of something like a glacier depends on what framework you are working with. Just a thought. Pfly (talk) 03:53, 28 January 2008 (UTC)

Prehistoric love

I'd like to know more about this [3] archaeological finding. Thanks. --Taraborn (talk) 20:38, 27 January 2008 (UTC)

A bit more context such as where/when may help getting you a detailed answer.. if you can provide it. (Otherwise those two 'things' are skeletons - the inorganic remains of human beings in what is often called a 'dual burial').83.100.183.193 (talk) 20:58, 27 January 2008 (UTC)

[4], ,this one ? Mion (talk) 21:25, 27 January 2008 (UTC)

Yeah, that one. Thanks. --Taraborn (talk) 22:01, 27 January 2008 (UTC)

Double burials are not uncommon -- google for the term. The two individuals may be siblings, and other same-sex pairs may be lovers. In the end it is impossible to know, and we "read" a lot of our cultures into the cold objects. For a descriptive example in ficiton: Jean M. Auel used the archeological record of a double burial in her prehistoric novel The Plains of Passage. BrainyBabe (talk) 09:09, 31 January 2008 (UTC)

What do dogs search for?

When a dog walks around searching for exactly the right place to do its business, what is it really searching for? —Preceding unsigned comment added by 216.47.188.16 (talk) 21:28, 27 January 2008 (UTC)

As I understand it they are smelling around for scents and finding a place to 'mark their territory'. See here (http://www.hsus.org/pets/pet_care/our_pets_for_life_program/cat_behavior_tip_sheets/urinemarking_behavior.html) and here (http://home.howstuffworks.com/how-to-solve-dog-behavioral-problems10.htm) ny156uk (talk) 22:41, 27 January 2008 (UTC)

Does that mean if they do it in the wrong place that it may send the wrong signal and start a fight? —Preceding unsigned comment added by 71.100.3.254 (talk) 13:33, 28 January 2008 (UTC)

From what I know, yeah. If two dogs' territories overlap or border, or one starts marking an other dog's territory as his own, and the dogs perceive themselves (via this smell communication) as hostile, then they bark and growl at each other, and do who knows what else. There used to be a term for this olfactory communication, but I forgot it. --Ouro (blah blah) 14:50, 28 January 2008 (UTC)

That would be the pheromones. See this for an example of what could happen when an animal wees in the wrong place (and also what Rockpocket does for a living when he isn't killing time on the Ref Desks). Rockpocket 07:34, 29 January 2008 (UTC)

Calendar calculation

Taking into account the changes from the Julian calendar to the Gregorian calendar what would the date as we know today as June 16 be in the 14th century in Europe?--Doug ^talk 21:51, 27 January 2008 (UTC)

June 16th (Gregorian) = June 8th (Julian) in the 14th century (not including 1400, when it's June 7th), according to any number of online calendar converters. Algebraist 22:19, 27 January 2008 (UTC)

Thanks. Would that mean then that June 24 (Gregorian) = June 16th (Julian) in the 14th century? The Julian calendar was the one used in the 14th century, correct?--Doug ^talk 23:31, 27 January 2008 (UTC)

Yes and no. I'm assuming this is related to the Giovanni Boccaccio question at the Humanities desk. If you're interested in counting in exact 365- or 366-day periods between one event and another, then you'd say that exactly 695 such periods elapsed between 16 June 1313 and 24 June 2008. However, if Boccaccio was born on what was called "16 June" in 1313 (and we don't know that he was), then 16 June would still be his date of birth, not 24 June. That's because the Gregorian calendar was not applied retrospectively to 15 October 1582, the date it was introduced, and all Julian calendar dates prior to 15 October 1582 are still correct and valid. If Boccaccio had in fact been born on 24 June 1313 (the feast day of St John the Baptist) under the then-existing Julian calendar (and, again, there's no evidence for this), then we'd still say his date of birth was 24 June 1313, even though 695 full "years" wouldn't be finished until 2 July 2008. -- JackofOz (talk) 23:57, 27 January 2008 (UTC)

If you will also be dealing with dates at other times of year, note that the year itself may not be what you expect, as the year typically did not start on January 1 and the date when it did start varied from place to place. For example, the date we would call April 1, 1366, at the time in England would have been March 24, 1365, and the following day (the first of the new year) would have been March 25, 1366. Sometimes you will see the notation "March 24, 1365/66" used to remind you of this problem. --Anonymous, 00:00 UTC, January 28 (Gregorian), 2008.

"... the date we would call April 1, 1366 ..." - I disagree with that part of your answer, Anon, on two counts. (a) Regardless of whether the year was called 1365 or 1366, the day was called 24 March by the folks back then, and that is still the only correct way to refer to that day now. (b) You seem to be extrapolating by use of the proleptic Gregorian calendar, however this is a pointless exercise. Dates in the Julian calendar prior to 15 October 1582 were not adjusted, and shouldn't be, otherwise there'd be calendric chaos. There was a disjunct between the calendars, which is what the 10-day gap was all about. The Julian calendar applied right up till 14 October 1582 and the Gregorian commenced at midnight leading into the 15th. Essentially, the Gregorian calendar is as irrelevant to dates prior to the 1582 changeover as the Julian is irrelevant to dates after the changeover. If we were discussing a date between 1582 and 1752, when the UK adopted the Gregorian calendar, you'd be right to bring OS and NS dating into the equation, but we weren't. -- JackofOz (talk) 03:30, 29 January 2008 (UTC)

True. I should have said something like "that, extrapolating backwards by the calendar we now use, would be called." --Anon, 02:27 UTC (copyedited later), January 30 (still Gregorian), 2008.