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

From: Richard Damon (rdamon_at_[hidden])
Date: 2002-04-23 22:15:00

> -----Original Message-----
> From: boost-admin_at_[hidden] [mailto:boost-admin_at_[hidden]]On
> Behalf Of Jeff Garland
> Sent: Tuesday, April 23, 2002 4:27 PM
> To: boost_at_[hidden]
> Subject: RE: [boost] Re: reminder about Date/Time formal review

...
> > 3.  The Gregorian calendar system needs more documentation.
> The Gregorian
> > calendar isn't a simple system, and there are a lot of things
> not documented
> > about GDTL's implementation of this system.  For example,
> historical dates
> > in a Gregorian system are dependent not only on the date, but
> also on the
> > location.  To clarify, different geographical locations adopted the
> > Gregorian system at different times, and this effects
> historical dates.  The
> > two most common "change over dates" used in gregorian date
> algorithms are
> > Oct. 4, 1582 and Sept. 14, 1752.  I think it's important to
> document which
> > "change over date" is used, since date projections before this
> date are not
> > accurate.
>
> Agreed.
>
> > (Trivia related to the above:  Did you know that Sept. 2, 1752
> was followed
> > by Sept. 14, 1752?  Or that George Washington's birthday, which we give
> > today as Feb. 22, 1732 was recorded on that day as Feb. 11, 1731?  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.

Gregorian (Sept 14, 1752)-1 = Gregorian(Sept 13, 1752) = Julian(Sept 2,
1752)

In America this date would have been written in Julian dates, in Holland in
Gregorian dates. Do not confuse the complication of determining which
calendar was in use with making a calendar system more complicated. What
would be complicated would be a "local calendar date" calendar, which would
be a function of where, and when (and possibly even for what use) the date
is expressed for.  The what use comes because the Julian Calendar originally
changed years in March, but for some purposes it was being changed to change
on January 1st, because of this sometimes dates in January and February were
given a double year like 1705/06. The Gregorian calendar always began in
January.