On 09-Jan-2009, Paul Eggert wrote:
msb@vex.net (Mark Brader; please reply accordingly) writes:
As you would know, there is a system of "military" time zone designations where zones are identified by a single letter: http://www.timeanddate.com/library/abbreviations/timezones/milit ary/ gives letter equivalents for zones from -12 = Y to +12 = M.
I was having an email conversation with Russ Rowlett, who maintains the units-of-measurement site at <http://www.unc.edu/~rowlett/units/>, and we were wondering whether these single-letter designations are actually still used in practice -- and, if so, how time zones above +12 or not on integer hours are represented. Is there an +official reference for current practice on this anywhere?
Yes, please see the Combined Communications-Electronics Board general communication instructions, dated 2007 <http://www.jcs.mil/j6/cceb/acps/acp121/ACP121H.pdf>. These are authoritative for the armed forces of Australia, Canada, NZ, the UK, and the US.
Briefly: "N" is also used for UTC+13, "to provide for a ship in zone -12 keeping Daylight Saving Time". There's no official provision for UTC+14, but I presume that'd be "O". For DST, use the corresponding next letter (e.g., the eastern-US "R" becomes "Q" during DST.)
I'm not 100% sure, but I think this is a change from past practice (though that is probably not important any more). When I was in the U.S. Army in the late 1960's, I am sure we used to affix "+1" to the base letter for a zone to indicate that it was DST, that is, for the U.S. Eastern time zone "R", during the observance of DST, we would write "2200R+1" not 2200Q. This was based on the zones labeled with the letter designations on a chart much like that shown on page 3B-2 of the referenced publication. Also note that the usage of 0000 is deprecated in the referenced publication, and that it would appear that 2400 (of the earlier date) would be the approved way of indicating a timestamp for something occurring exactly at midnight. This is the opposite of the current internet practice. (We should try, I believe, try to accommodate time stamps of 2400 and be able to specify 24 as a valid hour in time zone rules. Times after 2400, however belong to the new day and should be written, e.g., as 000015 for 15 seconds after midnight.)
As for non-integer hours, the instructions simply say: "For time midway between zones, both letters are used."
I read that as meaning a time exactly halfway between two integer zones. I don't think it's meant to account for a time that's, e.g., 8:45 ahead of UTC. One more point. The hour offsets of the lettered zones with respect to UTC are the opposite of the usual internet usage. "R" for the U.S. Eastern time zone, means +5, but the normal internet indication for that zone is -0500. Regards, Dave C. -- Dave Cantor Groton, CT 06340-3731 Dave@Cantor.mv.com