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/military/ 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.) As for non-integer hours, the instructions simply say: "For time midway between zones, both letters are used."