Paul Eggert said:
Michael H Deckers via tz wrote:
The definition of the tm_isdst flag does not even mention standard time
True, but other parts of POSIX make it clear that when tm_isdst is zero, standard time is intended. See:
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_...
and look at the TZ environment variable: POSIX says that its first few letters correspond to standard time and that later letters correspond to daylight saving time.
Actually, it says "the alternative timezone", with "Daylight Savings Time" being an *example*.
But the POSIX TZ requirement is that tm_isdst must be zero during standard time,
Right.
so if IST denotes standard time then current Irish rules should be represented by something like POSIX TZ='IST-1GMT0,M10.5.0/2,M3.5.0/1'.
Looks right.
any dictionary tells us that daylight-saving time is advanced, and not retarded, over the time used otherwise,
Dictionaries are descriptive, not prescriptive, in English.
Although that's typical I doubt whether we can take it as an axiom, as POSIX clearly allows DST to be retarded.
Specifically, the same definition of TZ allows any offset for the alternative timezone; one hour ahead of the standard zone is merely the default. If it could only be forwards of the standard zone, there would be wording saying so. -- Clive D.W. Feather | If you lie to the compiler, Email: clive@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646