"Andrew Bartley" <abartley@evolvosystems.com> writes:
> I'm having trouble calculating a date of April 1 2002.
What is the daylight savings transition day in your timezone?
(I'm betting March 31.)
> It seems as though the "+ interval('1 day'))" only adds 23 hours rather tha=
> n 24.
No, interval('1 day') is exactly 24 hours. But March 31 is longer than
24 hours. You're computing March 31 23:00 hours, and then truncating
that back to March 31.
If you want to calculate at the date level I'd suggest calculating with
dates, not timestamps.
regression=# select date('2002-03-31') + 1;
?column?
------------
2002-04-01
(1 row)
regards, tom lane