Scott Marlowe wrote:

> True. But that's only because it doesn't have a date to work against.
> If you run:
>
> select '2007-02-01 12:00:00'::timestamp + '1 month'::interval;
> you get: 2007-03-01 12:00:00
>
> If you run:
> select '2007-03-01 12:00:00'::timestamp + '1 month'::interval;
> you get: 2007-04-01 12:00:00
>
> Then, if we run:
> select ('2007-03-01 12:00:00'::timestamp + '1 month'::interval) -
> '2007-03-01 12:00:00'::timestamp;
> we get: 31 days
>
> But if we run:
> select ('2007-02-01 12:00:00'::timestamp + '1 month'::interval) -
> '2007-02-01 12:00:00'::timestamp;
> we get: 28 days
>
> So, I'm not sure how many days a month has.

Try looking at a calendar.;-)

You will find that these are the exact days between the two dates. Feb
has 28 days, so 1st of feb plus 1 month puts you at 1st of march

march has 31 days so 1st of march plus 1 month puts you at 1st of april.

Try a leap year -

select ('2008-02-01 12:00:00'::timestamp + '1 month'::interval) -
'2008-02-01 12:00:00'::timestamp;
?column?
----------
29 days
(1 row)


--

Shane Ambler
pgSQL (at) Sheeky (dot) Biz

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