cal program on UNIX systems is wrong!!

[Felix Lee]

Yes, the Gregorian calendar was decreed in the sixteenth century.  The
Germanic states did not adopt it until the seventeenth century.
England and its colonies did not adopt it until the eighteenth
century.  A side effect of the Protestant Reform.  Papal Bulls are
binding only to Roman Catholics.

Calendars and dates are not particularly straightforward.  Muslim,
Jewish, and Chinese calendars are still in common use.  And consider
curiosities, such as the French Revolutionary calendar.

For modern astronomical purposes, it's as well to calculate Julian
day number using the Gregorian calendar as decreed.
--
Felix Lee	flee at shire.cs.psu.edu	*!psuvax1!flee