RE: Why are there 365 days in a year?

[Mangetout]

somebody told me that the riots were also because people thought they were being cheated of 10 days from their lives, not sure if that’s what they really thought though.

[Achernar]

I’m fairly sure that the switchover between which calendar was official came at different times in different regions. I’m less sure that 1582 is the approximate year for switchovers in Europe, and that 1752 was the year in what would later become the United States.

[Triskadecamus]

[http://www.infoplease.com/spot/gregorian1.html"]Here]( [url) it says the British Calendar Act of 1751 became effective on September 2, 1852. Pope Gregory’s papal bull of February, 1582 decreed that 10 days should be dropped from October 1582 so that 15 October should follow immediately after 4 October, and from then on the reformed calendar should be used. Protestant countries ignored the order.

Tris

“Don’t let it end this way. Tell them I said something.” Pancho Villa’s last words

[Triskadecamus]

It would make me look ever so clever if a nice mod were to fix that darned link, and then delete this post.

Tris

“Swat my hind with a mellon rind, That’s my penguin state of mind.” ~ Opus

[Astroboy14]

Hey Chrystie, go Here for a nice surprise…

[APB]

*Originally posted by Mangetout *
**somebody told me that the riots were also because people thought they were being cheated of 10 days from their lives, not sure if that’s what they really thought though. **

The oft-repeated claim that the switchover in Britain in 1752 was accompanied by riots is now thought to be a myth. The idea seems to derive solely from Hogarth’s 1754 painting and engraving, The Election Entertainment. There were a few teething problems at the time, mainly because of some confusion over the dates of certain markets and fairs, but no evidence of any actual riots. The Act had foreseen and made provision for the main problem, which was landlords charging tenants for the ‘lost’ days.

[MHand]

[Nitpick]

By definition, a mean solar day is exactly 24 hours long.

This is how time used to be defined (86000 seconds per mean solar day). With this definition of a second, some seconds are longer or shorter than others, if the earth’s rotation slows or speeds up.

In 1967 the second was redefined to be 9,192,631,770 periods of vibration of the radiation emitted at a specific wavelength by an atom of cesium-133. Thus there aren’t exactly 24 hours in every ean solar day under the new definition.

One Source: http://www.encyclopedia.com/articlesnew/11650.html

[/Nitpick]

Lemme just add that others use different years. The Jews use a hybrid lunar/solar calendar with a great system of leap years and months which I was taught repeatedly in Sunday school and promptly forgot. All I remember is something about Adar Aleph and Adar Bet, but I don’t remember how often they add the extra leap month.

Muslims and the Chinese use a strict lunar calendar, based on the moon’s 4 week cycle. This is why Chinese New Year and Ramadan shift in the seasons. Or something like that. I’m a biologist, I really shouldn’t be answering these.

The Islamic Calendar shifts, as each year has a fixed number of lunar months. The Chinese Calendar does not shift like this. Like the Hebrew Calendar, the Chinese calendar has 12 and 13 month years in a pattern that ensures that the same months stay close to the same seasons for all time.

The Chinese Calendar is astronomical, not calculated. Thus, you can’t technically predict the future. Modern science is pretty good about calculating when future Chinese new years will be, but if some large comet changes the earth’s orbit slightly, it could eventually make calculated future Chinese calendar dates incorrect. the Chinese calendar, by definition, changes based on the earths orbit change, to ensure that months stay in their seasons.

The modern Hebrew Calendar is calculated. Because of slight error, it will eventually fall off from its seasons. The mean Passover date moves 1 day closer to winter ever 216 years. Don’t worry, say the religous Jews. Before this becomes a problem, the Messiah will come, and there will be a switch back to an astronomical calendar, as was done in ancient times.

[RM_Mentock]

*Originally posted by tracer *
**There are other definitions of the year, such as the anomalistic year, which is the amount of time it takes the Earth to go all the way around its elliptical orbit once, i.e. from one perihelion (or one aphelion) to the next. Unlike the tropical year, all anomalistic years are exactly the same length, so there is no need to compute a “mean” anomalistic year. **

The anomalistic year is 365.25964 days long[1], and I’d be very surprised if it were exactly the same every year. But with all the nitpicking, I am even more surprised that no one has mentioned that the earth actually takes 365.25636 days to go around the sun. That’s the sidereal year.

[ZenBeam]

edwino wrote:

You may remember that 2000 was a leap year, but 1900 was not. If we had a leap year every 4 years, every year would average 365.25 days. To correct for the difference between the actual 365.2422 and 365.25, you miss a total of 9 leap years over 1000 years.

I’m surprised no one else caught this one. The rule is no leap day if the year is divisible by 100, unless the year is divisible by 400. So you miss 3 leap years every four hundred years, not 9 every 1000 years.

I’m not going to bother updating the rest of the calculations in the post.

[cmkeller]

edwino:

All I remember is something about Adar Aleph and Adar Bet, but I don’t remember how often they add the extra leap month.

7 times in a 19-year cycle. I believe that it’s years 3, 6, 8, 11, 14, 17 and 19 of that cycle.

[edwino]

Goes to show. Biologists should not post on calendar questions. I was just bored.