Re: New date bug [Re: Correcting AGE_INFO]
Re: New date bug [Re: Correcting AGE_INFO]
- Subject: Re: New date bug [Re: Correcting AGE_INFO]
- From: "Mark J. Reed" <email@hidden>
- Date: Fri, 5 Feb 2010 08:04:06 -0500
sorry for the double reply, Nigel. Originally replied just to you...
On Fri, Feb 5, 2010 at 6:43 AM, Nigel Garvey
<email@hidden> wrote:
> In my message of Thu, 4 Feb 2010 13:57:53 +0000, I wrote:
>
>> property refMonday : date "Monday 1 January 1000 00:00:00"
>
> Bert has pointed out to me off-list that the 1st January 1000 was a
> Wednesday, which accords with my own memory(!).
Everyone who was around for the year 1000 would agree with AppleScript
that the 1st of January that year was a Monday.
If you project our current calendar (with modern leap year rules)
backwards, the day that gets labeled January 1st, 1000 is a
Wednesday, but the folks who were alive on that Wednesday would have
called it December 27th, 999.
The leap year rules changed because it turns out the tropical year is
not quite 365ΒΌ days, so the dates were getting out of sync with the
seasons (v-e-r-y s-l-o-w-l-y, but enough to concern Christian
authorities because the rules for calculating Easter are tied to the
assumption that March 21st is the equinox). The difference is that
centennial years not divisible by 400 are not leap years in the new
system - so 1900 wasn't a leap year, and 2100 won't be, either. Every
time you cross one of those years, the
difference between the two calendars increases by a day. (Or
decreases, if you're counting backwards.)
AppleScript seems to use the historical calendar rather than
retrojecting the modern one. That means it must be locale-dependent,
however, because different places adopted the new rules at different
times Catholic countries changed over in 1582; England and her
colonies didnt' change until 1752; Russia and China didn't change
until the Communists took over, which is why the revolution that took
place on November 7, 1917 from our point of view was called by them
the October Revolution.
The calendar with the old leap-year rule (every fourth year is a leap
year, period) is called the Julian (or "old style", abbreviated "O.S."
in dates) calendar; the new one is called the Gregorian (or "new
style", "N.S.") calendar. Some Eastern Orthodox congregations still
use the Julian calendar for determining the dates of Christmas and/or
Easter; the difference stands at 13 days (until the year 2100), so
that today is January 23rd, O.S.
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