This package consists of a C library and a Perl module (which uses
the C library, internally) for all kinds of date calculations based
on the Gregorian calendar (the one used in all western countries
today), thereby complying with all relevant norms and standards:
ISO/R 2015-1971, DIN 1355 and, to some extent, ISO 8601 (where
applicable).
(See also http://www.engelschall.com/u/sb/download/Date-Calc/DIN1355/
for a scan of part of the "DIN 1355" document (in German)).
The module of course handles year numbers of 2000 and above correctly
("Year 2000" or "Y2K" compliance) -- actually all year numbers from
1 to the largest positive integer representable on your system
(which is at least 32767) can be dealt with.
Note that this package projects the Gregorian calendar back until
the year 1 A.D. -- even though the Gregorian calendar was only
adopted in 1582 by most (not all) European countries, in obedience
to the corresponding decree of catholic pope Gregor I in that year.
Some (mainly protestant) countries continued to use the Julian
calendar (used until then) until as late as the beginning of the
20th century.
Finally, note that this package is not intended to do everything
you could ever imagine automagically for you; it is rather intended
to serve as a toolbox (in the best of UNIX spirit and traditions)
which should, however, always get you where you want to go.
WWW: http://search.cpan.org/dist/Date-Calc/
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