Re: [boost] Re: reminder about Date/Time formal review

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-04-26 10:34:43

At Friday 2002/04/26 06:33, you wrote:
>----- Original Message -----
>From: "Victor A. Wagner, Jr." <vawjr_at_[hidden]>
>To: <boost_at_[hidden]>
>Sent: Friday, April 26, 2002 1:13 AM
>Subject: Re: [boost] Re: reminder about Date/Time formal review
>
>
> > Adding to the pedantry, my reference "Supplement to the American Ephemeris
> > and Nautical Almanac"

oops... "Explanatory Supplement......"

>  Britain and what is now the U.S.  (it wasn't the
>U.S.
> > in 1751) adopted the Gregorian calendar on the same day, so July 4, 1751
> > was the same day both in England _and_ the colonies.... by implication,
> > July 4th 1752 was ALSO the same day.
>
>OK, this I did not know.  I'm not aware of when the various regions adopted
>the Gregorian system.
>
> > At Wednesday 2002/04/24 07:37, you wrote:
> > >[deleted]
> > >Gotta
> > > > > > love this date stuff, no?)
> > > > >
> > > >
> > > > Wrong. Gregorian dates are not dependant on where your are in this
>way.
> > >What
> > > > is dependant is which colander was in use.
> > >
> > >July 4, 1751 in the US was a very different day then July 4, 1751 in
> > >England.  The reason, as you point out (and I thought was obvious from
>what
> > >I posted) is because the US didn't adopt the Gregorian system until Sept.
> > >14, 1752... or, more precisely, they adopted it on Sept. 2, 1752, which
> > >immediately became Sept. 14, 1752.  The point is, you can't project dates
> > >backwards with out knowing the location as well as the date.  Further,
>the
> > >"change over" date also effects this.  If the change over date used by
>the
> > >system were the American Sept. 14, 1752 this would mean the algorithm
> > >doesn't take into account things such as the missing day added at this
>time
> > >when dates are projected further back.
> > >
> > > > Gregorian (Sept 14, 1752)-1 = Gregorian(Sept 13, 1752) = Julian(Sept
>2,
> > > > 1752)
> > >
> > >The above isn't accurate.  Gregorian (Sept. 14, 1752) - 1 = Gregorian
>(Sept.
> > >12, 1752)
> >
> > Ummm, I think you mean Gregorian(Sept. 13, 1752) .... not 12
>
>No, I meant 12.
^^^^^^^^^^^^^^^^^^^^

> > >if you were in one of the regions that adopted the Gregorian
> > >calendar in 1582, or Julian (Sept. 2, 1742) if you were in America or one
>of
> > >the other locations that was still using the Julian calendar.  The
>problem
> > >is that the Gregorian calendar has not been a stable system, with 10 days
> > >being added to the Julian system in 1582 and 11 days being added in 1752
> > >when America switched over.
> >
> > There weren't 11 days "added" to the Gregorian calendar in 1752, the
> > Gregorian calendar and the Julian calendar were the 11 days apart (as
> > opposed to 10 days apart in Oct 1582 when pope Gregory decreed the
>original
> > change).  I have no idea what you mean by "not been a stable system"
>
>This contradicts the sources I have, but I'm not a domain expert.

I'd be interested in any source(s) which seem to assert that there was an 
"extra day" removed from the Gregorian calendar in September, 1752; this is 
something I've not previously heard asserted.

>Bill Kempf
>_______________________________________________
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Victor A. Wagner Jr.      http://rudbek.com
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