times, dates, images, and S-W

[Guy Steele <cbmvax!uunet!think.com!gls>]

   Date: Mon, 3 Sep 90 10:35:42 +0800
   From: major@pta.oz.au (Major)


   dave@PRC.Unisys.COM writes:

   >   A big advantage is that numerical sorts work just fine.
   >

   >   [defending his suggestion for date layout]
   >   Another advantage is that it doesn't favor either American-style dates
   >   (mm/dd/yy) or British-style dates (dd/mm/yy)

   No, it favors Japanese-style dates yymmdd or yy.mm.dd

   >   it's more logical than either, and it can be equally easily explained
   >   to members of both groups.

   The American method mirrors the way we pronounce the date
	   010290		January second 1990

   The British method is ascending order of significance and the Japanese
   descending order of significance.

   The British or Japanese seem more 'logical' (I hate using that word in this
   group) to me but ease of computer sorting is not enough of a tie-breaker
   for me to say that the Japanese way is a clear winner.

Consider that the order yy mm dd puts the fastest-varying position
last.  This is consistent with our usual notations for time
(hh:mm:ss) and for ordinary numerals.  As you count successive
integers (18, 19, 20, 21, 22) the last position changes fastest, the
second-last position changes second-fastest, etc.  The same is true
if you generalize to decimal fractions.  If you have a date and a
time together, only the order yy/mm/dd hh:mm:ss gives you this useful
property.

Probably a date ought to be preceded by a marker of
some kind so that you know what is coming, carrying the
force of "A.D." and "B.C." (or "C.E." and "B.C.E.").
Perhaps a time should be preceded, at least optionally,
by a time zone indicator.

	AD 1990 September 4 EDT 13:12:47

--Guy Steele