Re: BUG #12739: to_timestamp function conver string to time incorrectly - Mailing list pgsql-bugs

From Tom Lane
Subject Re: BUG #12739: to_timestamp function conver string to time incorrectly
Date
Msg-id 27550.1423264369@sss.pgh.pa.us
Whole thread Raw
In response to BUG #12739: to_timestamp function conver string to time incorrectly  (lstrupinskaya@gmail.com)
List pgsql-bugs
lstrupinskaya@gmail.com writes:
> When trying to use to_timestamp function to convert string '3/10/2013 2:30'
> to timestamp it was actually converted into 3/10/2013 3:30.

> Below is select statement:

> select to_timestamp('3/10/2013 2:30','MM/DD/YYYY HH24:MI');

If you're running with USA DST rules, there was no such thing as 2:30
observed local time on that date: clocks advanced from 1:59:59 to 3:00:00.

As documented, Postgres handles invalid or ambiguous times near a DST
transition by supposing that the given time is local standard time.
So in the New York zone for instance, 2:30 local standard time (GMT-5)
would equate to 3:30 local daylight time (GMT-4), and daylight time would
have been what was observed at that instant, so that's what gets printed.

If you don't want DST-aware handling of timestamps, don't use type
timestamptz nor to_timestamp (which actually produces timestamptz).

            regards, tom lane

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