Default time zone for a location (previously Europe/London)

Oscar van Vlijmen ovv at
Tue Sep 5 12:03:20 UTC 2006

> From: Paul Eggert
> Subject: Re: Europe/London
Or more appropriately:
> Subject: Re: Default time zone for a location (previously Europe/London)

> "Srdjan Krajnalic" writes:
>> However GB-Eire starts with a 1916 rule, leaving anything from 1847 until
>> 1916 seemingly undefined.
> Until the first rule applies, you use the first-listed rule that
> is on standard time (in this case, "GMT" with UTC offset zero).
> Unfortunately I don't see this point being covered clearly in the
> zic man page.

I believe a similar situation was mentioned by me on 2004-05-17.
If a Zone line gives a DST Rule, but no valid Rule can be found, then what?

Example Korea:
The last Rule lines:
Rule    ROK    1987    1988    -    May    Sun>=8    0:00    1:00    D
Rule    ROK    1987    1988    -    Oct    Sun>=8    0:00    0    S
Some Zone lines:
Zone    Asia/Seoul    8:27:52    -    LMT    1890
            8:30    -    KST    1968 Oct
            9:00    ROK    K%sT

For periods starting 1989 there is no valid Rule.
The answer given by 'ado' May 2004 was:

Remember that the Rules tell when DST transitions happen; in the above case,
the Rule that's valid is one that specifies the last transition before May
2004 [read: today], which is assumed to be in effect in perpetuity.
Generally speaking, we want to have the last line of a Zone refer to a Rule
line. This is particularly important in cases where a country has multiple
time zones.
If the country decides in the future to change the way DST is handled (for
example, decides to start observing DST again), we can make things right by
changing one Rule rather than by changing multiple Zones.

Maybe this repeated information helps writing clarifications for the manual.

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