cal program on UNIX systems is right!!

[Doug McIlroy]

<	... the special case [of "cal"] stated in the manual, namely
<	that in September, 1752 11 days were dropped from the
<	calendar is absolute garbage!!

<	Calendar reform did not occur as late as 1752, even in
<	Britain and the US.  Rather, calendar reform occurred nearly
<	two centuries earlier when Pope Gregory decreed that
<	throughout Christendom, the day following October 4, 1582
<	would be October 15. ... If you wish references ... I suggest
<	the Astronomical Almanac published jointly by the US Naval
<	Observatory and the Royal Greenwich Observatory. ... Obviously
<	there was no astronomer around when this particular program
<	was written.

<	Arnold Gill
<	Queen's University at Kinsgton
<	Arnold.Gill at QueensU.CA

Mr. Gill, if an intemperate fool deserves such polite address,
is no calendric wizard.  Had he consulted even the most elementary
reference he would have known that the calendar did not change 
overnight.  Below, for his instruction is what the Britannica
says on the subject.  The UNIX calendric routines were based,
however, on a higher authority: the Explanatory Supplement to
the Nautical Almanac, which covers the topic in much more
elaborate detail.  Unlike Mr. Gill, the authors of UNIX
owned an almanac to read rather than to brandish.

	In France, Italy, Luxembourg, Portugal, and Spain, the
	New Style calendar was adopted in 1582, and by most of the
	German Roman Catholic states as well as by Belgium and part
	of the Netherlands by 1584.  Switzerland's change was
	gradual, beginning in 1583 and being completed only in
	1812. Hungary adopted the New Style in 1587, and then
	there was a pause of more than a century before the
	first Protestant countries moved over from the Old Style
	calendar.  In 1699-1700, Denmark and the Dutch and
	German Protestant states embraced the New Style, although 
	the Germans declined to adopt the rules laid down for
	determining Easter [to which they acceded] only in 1776.
	Britain adopted the New Style in 1752 and Sweden in 1753,
	although, because the Swedes had in 1740 followed the
	German Protestants [about] Easter, they declined to
	adopt the Gregorian calendar until 1844.  Japan adopted
	the New Style in 1873; Egypt in 1875; and between 1912
	and 1917 it was accepted by Albania, Bulgaria, China,
	Estonia, Latvia, Lithuania, Romania, Turkey, and
	Yugoslavia.  Soviet Russia adopted the New Style in in
	1918; Greece in 1923.

	In Britain and the British dominions, the change was
	made when the difference between the New and Old style
	calendars amounted to 11 days, by naming the day after
	September 2, 1752, as September 14, 1752; but there was
	much public misunderstanding, and in Britain rioters
	demanded ``give us back our 11 days,'' even though
	legislation authorizing the change had been framed to
	avoid injustice and financial hardship.  Alaska retained
	the Old Style calendar until 1867, when it was
	transferred from Russia to the United States.

If I recall correctly, some of those rioters put it more colorfully,
``Give us back our fortnight.''  And George Washington, whose
birthday was celebrated in the US on February 22 until it
became demoted into an anonymous Monday shopping spree,
was born on February 11.  That fact, too, is in the Britannica.

Perhaps Mr. Gill thinks the calendar had to change in 1582
because the Pope was infallible.  But the doctrine of 
infallibility was not defined until the Vatican Council of
1869-1870.

Now, had Mr. Gill been clever, he'd have asked how the cal
program may be modified to cope with ``internationalization.''

Doug McIlroy
AT&T Bell Labs
doug at research.att.com