Jim Nasby <j...@nasby.net> writes:
> On Jul 19, 2011, at 11:22 AM, Ian Caulfield wrote:
>> There was an earlier point made that if someone puts eg 5pm local time
>> two years in the future into the database, and then the DST boundary
>> gets moved subsequently, some applications would like the value to
>> still say 5pm local time, even though that means it now refers to a
>> different point in absolute time - this potentially seems like a
>> useful feature. Retroactive timezone changes wouldn't make a lot of
>> sense in this case though...
> Right; and timezone's aren't supposed to change retroactively. The ZIC
> database is specifically setup so that it knows the history of TZ changes and
> deals with the past correctly.
You haven't noticed that at least two or three times a year, there are
"historical corrections" in the ZIC database? The mapping between local
time and UTC might be less likely to change for a time instant in the
past than one in the future, but it would be folly to assume that it's
immutable in either direction.
regards, tom lane
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