On 10/05/18 19:30, Vlad Khorsun via Firebird-devel wrote:
The key is that DST doesn't affect given time zone. TZ could be
"standard time" based (such as MSK)
or "DST based" (such as MSD or IST you speak about) but TZ itself is not
changed with DST start\end.
What is changed - is what TZ should be used. But we (I) speak not about it.
Officially a TZ 'timezone' defines unique set of rules for the OFFSET
changes for that 'location' and under the current practice, any timezone
that has the same rule set since 1970 has been merged to reduce the
number of identifiers used in TZ. Some of those rule sets DO diverge
prior to 1970, so unless you have an OS that is using the backzone file
the rule set used as a base will be used rather than the actual changes
to the offset for the merged rule sets.
In many cases timezone is used - incorrectly - to describe the offset
and not the set of rules plotting the changes to the offset.
--
Lester Caine - G8HFL
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