On Sun, 22 Sep 2013, Bill Seymour wrote:
A partly-baked idea to solve the more general problem of when zones appear and disappear: would it make sense to have another kind of entry in the zone RULES column to indicate that we should now follow another zone's practice? How about the keyword, Zone, a space, and the name of the other zone, with the next column following whitespace, if present, being the [UNTIL] column?
I liked the syntax proposed by Andy Lipscomb on 5 Sep 2013, with "=" as a magic character in the GMTOFF, RULES, and FORMAT fields of a Zone record. See <http://mm.icann.org/pipermail/tz/2013-September/019952.html>. He gave this example: Zone America/North_Dakota/New_Salem -6:45:39 - LMT 1883 Nov 18 12:14:21 =America/Denver = = 2003 Oct 26 02:00 =America/Chicago = = which would mean: America/North/Dakota/New_Salem used LMT until a specified date, then followed the same rules as America/Denver until a specified date, and now follows the same rules as America/Chicago into the future. --apb (Alan Barrett)