Re: [LEAPSECS] building consensus

From: John Cowan <>
Date: Mon, 5 Jun 2006 12:36:20 -0400

Zefram scripsit:

> There is the alternate point of view that the calendar in actual civil use
> in a particular locality, changing between different arithmetic calendars
> at different times, constitutes an unpredictable observational calendar.
> Perhaps we need a concept of "calendar zone" analogous to time zone,
> with a calendar zone database to match.

Claus T√łndering's excellent Calendar FAQ contains a first cut at such
a thing in Section 2.2.4. See
As one would expect, the information is less than 100% reliable, as
sources disagree.

I particularly like this one:

# Sweden has a curious history. Sweden decided to make a gradual change
# from the Julian to the Gregorian calendar. By dropping every leap year
# from 1700 through 1740 the eleven superfluous days would be omitted and
# from 1 Mar 1740 they would be in sync with the Gregorian calendar. (But
# in the meantime they would be in sync with nobody!)
# So 1700 (which should have been a leap year in the Julian calendar)
# was not a leap year in Sweden. However, by mistake 1704 and 1708
# became leap years. This left Sweden out of synchronisation with both
# the Julian and the Gregorian world, so they decided to go back to the
# Julian calendar. In order to do this, they inserted an extra day in
# 1712, making that year a double leap year! So in 1712, February had
# 30 days in Sweden.
# Later, in 1753, Sweden changed to the Gregorian calendar by dropping
# 11 days like everyone else.

Note that the Islamic calendar is truly observational: a month starts
when an actual human observer makes a lunar observation, and all
Islamic calendars purporting to show the future are merely best-effort
approximations. This calendar is official in some but not all Muslim
countries, even for civil purposes.

My corporate data's a mess!                     John Cowan
It's all semi-structured, no less.    
    But I'll be carefree              
    Using XSLT
Received on Mon Jun 05 2006 - 09:36:44 PDT

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