FW: Time Zone Data File Conventions

John Cowan cowan at drv.cbc.com
Thu Oct 16 18:44:12 UTC 1997

Wally Wedel wrote:

> I am just finishing up implementing some general time zone classes in
> Java. I parse your data files and build time zone classes from them.
> Consequently, I have a few questions.
> 1) You use the concepts of "wall clock", "standard", and "GMT" time in
> specifying transition times. I'd like to verify just what these mean.
> a) Does "wall clock" mean simply take the time as given applying no
> corrections?
> b) Does "standard" mean apply DST time shift to given time to find true
> time?
> c) Does "GMT" mean apply GMT offset to given time to get true time?

In essence, yes.  For example, all DST transitions in the U.S. are
defined by wallclock time: we transition at 2 AM defined by the
prevailing time before the transition.  Thus the EST "Spring Ahead"
transition occurs at 7 AM GMT, whereas the corresponding "Fall Back"
transition occurs at 6 AM GMT.

> 2) Is the convention for rule naming that when searching for the
> applicable rule, one looks for a rule with the specified name covering
> the specified date? I assume that failure to find a rule implies
> no time shift.


> 3) The comments in the data files contain quite important information
> about the actual coded information. Have you considered converting
> them to HTML to get them better tagged? I'm particularly interested
> in tagging some kind of a long name usable in reports and like.
> I've been trying to figure out how to preserve them
> in an OODB so that they are properly associated with the data they
> describe.

They are just plain text.  Remove the leading #, then any leading
spaces, but preserve the CR breaks, and associate the whole block
of comments with the following rule.

John Cowan	http://www.ccil.org/~cowan		cowan at ccil.org
			e'osai ko sarji la lojban

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