Eugene, On Fri, Feb 14, 2003 at 07:48:58PM +0100, Eugene van der Pijll wrote: > Dave Rolsky schreef: > > That's what Calendrical Calculations says. I'm wrong, they're right. > > It'll be fixed in the next release ;) > > It seems you're right; at least, most references on the internet agree. > And as we all know, the internet can't be wrong. > > But this leads to this question: should DateTime use the Gregorian > calendar before 1754 as it does now, or the Julian date? I can think of > arguments for both. > > If the first, I would like to see (and if necessary, write) a module > DateTime::Calendar::Christian::English, which uses the Julian calendar > until 1754. And 49+ other modules, each corresponding to a J-G switch.
I'd rather see a single module do this with some optional parameters defining the switching details. > Eugene > > P.S. I suspect you don't like the term Christian; does anyone know > another name for the combination of the Julian and Gregorian calendars? > CommonEra? AD? Since Pope Gregory XIII defined a certain day to be the first one the new method of numbering days should be used rather than changing past dates from that day, too, one could argue _the_ Gregorian calendar is in fact a combination like the one you suggest. The switch was to take place in October 1582, however. Note also that this calendar defines more than only day numbers and leap years. Its other concern are the dates of important Christian holidays, some of which are related to Hebrew holidays and thus to a moon cycle. It gives a pure-math definition, however, so that no astronomical observations are necessary to determine the dates of holidays for all the time this calendar will be in use. To some, it might make sense to put everything the Gregorian calendar defines in one place -- as I had in mind when I registered Date::Gregorian on CPAN. Thanks to C.F.Gauss we even have a nicely compact formula for the trickiest part, also known as Gaussian Easter formula. The credit for the original Gregorian calendar design goes to Joseph Justus Scaliger (1540-1609). Making one of those names part of a module name would perhaps be less likely to put people off who take offence from religious references. Personally, I'd vote for DateTime::Calendar::Gregorian, if it gives the complete thing, and DateTime::Calendar::GregorianYear or something if you insist on just the days and leapyear stuff. Martin
