[tz] Extended data format

Andy Lipscomb AndyLipscomb at decosimo.com
Thu Sep 5 14:46:10 UTC 2013

It seems, based on the discussions, that one desired feature of an "extended" notation is to be able to say "this zone is like that other zone during period X." Herein, a suggestion for notation to express that relation:

In a line of the zone record, the GMTOFF, RULES, and FORMAT fields may consist of an equal sign followed by the name of a zone. This has the meaning "use the data for the named zone in this zone as well." An equal sign standing alone repeats the most recent zone explicitly named in an equals-reference (which must be within the current zone record).

Examples, using zones already in the database, follow:

Zone America/North_Dakota/New_Salem -6:45:39 - LMT 1883 Nov 18 12:14:21
    -7:00    US    M%sT    2003 Oct 26 02:00
    -6:00    US    C%sT

would in this notation be expressed as

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       =    =

And America/Shiprock could be represented as

Zone America/Shiprock =America/Denver = NNT

(meaning that it always follows Denver's offset and DST rules, but uses the abbreviation NNT--the phrase "Navajo Nation Time" is in use).

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