On Wed, Nov 5, 2014 at 01:13:21PM -0500, Tom Lane wrote:
> Magnus Hagander <magnus@hagander.net> writes:
> > On Wed, Nov 5, 2014 at 7:02 PM, Bruce Momjian <bruce@momjian.us> wrote:
> >> Because 1500 % 100 == 0, I think 1500 was not a leap year.
>
> > I believe it was a leap year in the Julian calendar, maybe that's
> > where the difference comes from?
>
> Indeed. We won't be changing our code though, because we document that
> we follow Gregorian calendar rules even before that calendar was instituted
> (ie, proleptic Gregorian calendar). You could argue for doing that
> differently, but then what are you going to do for dates before the Julian
> calendar was instituted? In any case, this behavior appears to be
> required by the SQL standard, which repeatedly says that datetime values
> are "constrained according to the Gregorian calendar".
I have applied the attached C comment to document why we use the
Gregorian calendar for pre-1582 years.
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
