Re: Where do Christmas presents go?

On Wed, 14 Dec 2005 18:32:45 -0500, "Kevin J. Cheek"
<kevinc@xxxxxxxxxxxxxxxxxx> wrote in
<news:MPG.1e09d143df8c1a86989a72@xxxxxxxxxxxxxxxxx> in
rec.arts.sf.composition:

> In article <txvxh3aefp59$.5g6cyhwe597n$.dlg@xxxxxxxxxx>,
> b.scott@xxxxxxxxxxx says...

>> On Tue, 13 Dec 2005 22:38:21 -0500, "Kevin J. Cheek"
>> <kevinc@xxxxxxxxxxxxxxxxxx> wrote in
>> <news:MPG.1e0952b4e6390ffa989a71@xxxxxxxxxxxxxxxxx> in
>> rec.arts.sf.composition:

>>> In article <DeLnf.14803$O05.14549@xxxxxxxx>, jwkenne@xxxxxxxxxxxxx
>>> says...

>>>> It also suffers from being inadequate. The next
>>>> correction should have been at 2000. With a 4000-year
>>>> correction, after about 20,000 years, there will have
>>>> to be a double correction.

>>> There was a correction in 2000. All sesquicentennial years
>>> divisable by 400 are leap years. 1600 was a leap year.
>>> 1700, 1800, 1900 were not. 2000 was a leap year.

>> I imagine that John knows that. The Gregorian 400-year
>> correction is an overcorrection, and I suspect that he's
>> saying that 2000 ideally ought *not* to have been a leap
>> year.

> Overcorrection? Let's see:

Sorry: that should have been 'undercorrection'. Wrong word,
right logic. The Gregorian calendar yields on average year
of 365.2425 days, versus 365.25 for the Julian calendar.
The actual value is about 365.2422 SI days in a mean
tropical year, if I remember correctly. Google tells me
that the vernal equinox year is currently about 365.2424
natural days (and has been between 365.2423 and 365.2424
natural days for some time). Whichever one you're using,
this means that the Gregorian correction doesn't drop out
enough leap years. It is therefore possible in principle
that 2000 ought not to have been one.

> The earth's orbit is 11 minutes, 14 seconds shorter than
> 365.25 days. If we were on the Julian Calendar, by 2000
> we would have gained 3 days, 2 hours, 53 minutes, 20
> seconds since 1600. But on the Gregorian Calendar, 1700
> wasn't a leap year.

Why are you starting at 1600? When the change was made from
Julian to Gregorian, the one-time correction was a whole
number of days. I haven't checked, but it's very unlikely
that this was exactly correct, and if it wasn't, your
calculation accounts for only part of the accumulated error.
(By the way, I'm not defending John's claim, since I don't
know its actual basis; I'm merely pointing out that it isn't
prima facie absurd and that you haven't actually rebutted
it.)

While it doesn't really matter for this calculation, it
should be pointed out that we (Great Britain and colonies)
weren't on the Gregorian calendar in 1700.

> That removes one of those three days. 1800 wasn't a leap
> year. That removes another one of those extra days. 1900
> wasn't a leap year. That takes care of the last extra
> day. If we didn't have a leap year in 2000, our calendar
> would be a day behind the seasons.

> That also means that in 2000, our calendar was 2 hours, 53
> minutes, 20 seconds fast.

Relative to 1600.

[...]

Brian
.