There's work in progress on adding historical information to time zone files. It might be useful to extend the syntax of "UNTIL" parts so that you could write something such as # Zone NAME GMTOFF RULES/SAVE FORMAT [UNTIL] Zone This 0:00 - TST 1916 May 21 2:00s 0:00 Whatever T%sT 1968 Feb 18 2:00s->That where the "->That" on the final line means "after the UNTIL time, use whatever happens in Zone 'That'." This would both allow for more concise representation of historic information and allow a "-c" (or some other letter) flag to zic that would tell it to only compile "current" zones--zones that did NOT end with a line containing "->". If you have insights on whether this is the best thing to do, I'd love it if you'd share them with folks on the time zone mailing list. --ado