[tz] data not represented in tzfiles

Paul Eggert eggert at cs.ucla.edu
Fri Sep 6 03:05:29 UTC 2013

Zefram wrote:
> The extra information not in the tzfiles that you can get from the zic
> source is limited to things like whether a transition was the result of
> a long-term rule as opposed to a one-off decision, and what the rule was.
> I don't think this is really meaningful information for the purposes for
> which the zone data is intended.  It also doesn't look as if previous
> practice has tried to maintain this information in a meaningful way,
> other than perhaps in the comments.

That's correct.  In the data I've often coalesced repeated
entries into a single rule that explains these entries.
Usually these entries came from Shanks, so who knows how
reliable they are?  But sometimes they came from more-reliable
sources.  It's generally not that well-defined whether a series
of laws, some marked as extensions of others, constitute one
rule or several in the tz sense, and generally speaking I
coalesced them when I could.

Conversely, sometimes just a single legal rule (e.g., "first
Sunday in April unless that's Easter, in which case the second
Sunday") had to be split into multiple tz rules, since the tz
rules don't have the notion of Easter built-in, so I had to
enter each Easter manually as a special case.

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