Olson, Arthur David (NIH/NCI) said:
- Prior to the Julian conversion, different locales had different rules for when the number of the year changed. In and before 1752 in Great Britain, for instance, the number of the year changed on 25 March; 1-24 March belonged to the previous year! With the adoption of the Gregorian calendar, the change was universally 1 January.
It's not even that simple: - England and Wales used the March 25th rule, but Scotland used January 1st. - Some uses even in E&W followed the January 1st rule anyway (e.g. leap year determination). - The change wasn't synchronised with the Gregorian change, but happened a little earlier: 1751 began on Mar 24th but 1752 began on 1st January (thus, while 1752 lost 11 days, 1751 lost 83).
(For this reason, you'll sometimes see eighteenth-century dates as O.S. ("Old Style") or N.S. ("New Style") when the year would otherwise be ambiguous.
And the day, actually.
- As you correctly observe, leap years were observed irregularly in Rome in Republican and early Imperial times. In fact, they were so irregularly observed that it was occasionally necessary to intercalate entire months.
You're confusing the pre-Julian calendar (which used intercalary months) with the Julian one (which used leap days). It wasn't so much "irregular" as "erroneous" - leap days were inserted every *three* years in the period starting 46 BCE; when the mistake was spotted, several leaps had to be omitted. I *believe* that 45, 45, ... 9 BCE were all leap years, then there were 15 common years in a row, with 8 CE being the next leap year.
- I use a message catalog (the same catalog in which I hold localised month names) to hold a locale's Julian conversion date, and then select the catalog according to LC_TIME. Tcl's ordinary message catalog functionality can be used to change the date.
There may be more than one conversion date: Sweden converted twice (including a year which had a February 30th in it). -- Clive D.W. Feather | Work: <clive@demon.net> | Tel: +44 20 8495 6138 Internet Expert | Home: <clive@davros.org> | Fax: +44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 Thus plc | |