The change from the Julian to the Gregorian calendar necessitated a 10 or 11 day change in “what day is today?” This didn’t happened all at once, but started in 1582 and proceeded to ripple around the world, with some parts of China not adopting it until 1949. (All this is per ‘Calendar’ by David Ewings Duncan.)
My question (not answered in Calendar) is; did they just move the whole calendar forwards, or just increase the number of the day?
That is, assuming it occured on a Wednesday, was the next day a Thursday or a Sunday? (If I counted right) And have all countries done it the same way?
In Catholic countries, Thursday, October 4, 1582 was followed by Friday, October 15. The cycle of weekdays was not interrupted.
In Protestant Britain, and the still-British American colonies, Wednesday, September 2, 1752 was followed by Thursday, September 14 — synchronizing them with the Gregorian calendar already in progress. Other European nations switched on different dates, but I imagine in all cases it was a matter of joining the Gregorian calendar as-is, same weekday and all.
Well, if you believe this site, in Britain “(Wednesday) September 2, 1752 [was] followed immediately by (Thursday) September 14, 1752.”
This kind of makes sense when you think about the purpose of the Gregorian reform. Essentially, Caesar’s calendar got the number of days in a year slightly wrong, by having the wrong number of leap days (on average) per year. The adoption of the Gregorian calendar was designed to “fix” this yearly cycle, and make sure that the Earth got back to closer to the same place in its orbit every time January 1 rolled around. (Of course, they didn’t really think of it in these terms.) This annual cycle is completely independent from the cycle of the days of the week, so there was no reason to change that—and, presumably, good reasons from a religious perspective not to change it.
They possibly would, but so would the astronomers and the scientists and every person of ordinary common sense. The cycle of weekdays has nothing to do with the rotation of the earth around the sun, and there was absolutely no reason to make any adjustment to it.
It wasn’t, strictly speaking, even necessary to eliminate any dates from the calendar at all. With just the reform to leap days, the calendar would have been just as accurate, albeit with the vernal equinox near March 11. The primary reason to eliminate the days was to keep the vernal equinox, which is the point from which Easter is determined, from getting too close to Christmas. Or more precisely having enough time to have smooth changeover from a celebratory time to the penitential time of Lent.
Not quite, I think. The date on which Christmas is celebrated is, and was always known to be, arbitrary. Not so the date of Easter, which commemorates an event which supposedly occurred at Passover. And there is considerable theological signficance to this.
Now, of course, by the time of this controversy, the Christians are calculating the date of Easter in a way which differs from the method used by Jews to fix Passover, so the two events rarely coincide. But the two methods have enough in common to ensure they never drift too far apart or (and for the Christians this is the significant point) that the time of Easter continues to have a connection with Passover in first-century Palestine. Since this connection means something, it’s important to keep it in good order, so to speak, so the errors which have accumulated in the calendar since (notional) AD 1 are identifed and reversed.
But what is the significance of the equinox being around March 21? I’ve always thought that a more natural calendar would have the equinoxes on April 1 and Oct 1, and the solstices on Jan 1 and July 1.
The traditional dates for the solstices and equinoxes are March, June, September, and December 25, or at the least thereabouts. Now, the Julian calendar is off by about 1 day every 128 or so years, and so by the time of the Council of Nicea, which was in 325 AD, and which was also when the rules for the calculation of the date of Easter were more or less set, the dates had shifted to about the 21. So, the goal of the Gregorian calendar reform was to bring things back to what the dates had already shifted to at the time of Nicea.
To get a bit nitpicky, that the date of Christmas is on the traditional winter solstice is not arbitrary. It was the decision to celebrate it on the solstice that was arbitrary. But in either case, by 1582, the date was pretty much set in the liturgical calendar. You couldn’t change it any more then than you could now.
As for the determination of the date of Easter, it is true that that the Church uses a different mechanism than the Hebrew calendar, mostly to separate the two religions. But there was also a strong desire not to have the dates of Passover and Easter coincide too much, so the computus, which is the technical aspect of the calculation of the date, has some fudging in it to make sure that Easter is usually after Passover. This is reflected in the 10 days that were deleted from the calendar, which I believe was 1 day too many (it’s either that or 1 too few, and I’m too tired to figure that out right now), and some technical aspects related to addressing the inaccuracies in the Metonic cycle which dictates when the full moon is.
My point is that all this is possible to do without taking any days out of the calendar, and just “resetting” the date of the equinox. Which would have minimized the disruption to day-to-day life that a month of 21 days can cause.
It is possible that the Gregorian calendar was engineered to stay in step with the Hebrew calendar, but I don’t believe this is true. I believe, but can’t cite at the moment, that keeping the vernal equinox “accurate,” which is essential to the computus, on or near a set date was the driving force behind the changes to the calendar. This is circumstantial evidence, but the Wikipedia states “The Hebrew calendar year is longer by about 6 minutes and 25 + 25/57 seconds than the present-day mean solar year, so that […] about every 231 years it will fall a full day behind the Gregorian calendar year.” The rather large magnitude of this error suggests that agreement with the Hebrew calendar was not the intention of the Gregorian.
There was one place where the day of the week did not follow smoothly when changing from Julian to Gregorian calendars: Alaska.
Alaska was transferred from Russia (which used the Julian calendar) to the US (Gregorian calendar) on Friday, 18 Oct 1867. That’s the Gregorian date; the Russians who gave up control thought the day was Saturday, 7 Oct 1867. So Alaska jumped backward one day of the week when it was transferred.
The reason for this has to do with the relative placement of the national capitals. Alaska was ahead of the time in St Petersburg, while it was behind the time in Washington. So you may think of it as Alaska jumping to the other side of the International Date Line[sup]1[/sup].
[sup]1[/sup] I don’t think map makers put the IDL on maps at that time. But even if they did, it has no official standing. The IDL is just a convenience for map users.