How to get the number of days in a month?

Question

I am trying to get the following in Postgres:

select day_in_month(2);

Expected output:

28

Is there any bu

Answer 1

Note that expected output for day_in_month(2) can be 29 because of leap years. You might want to pass a date instead of an int.

Also, beware of daylight saving : remove the timezone or else some monthes calculations could be wrong (next example in CET / CEST) :

SELECT  DATE_TRUNC('month', '2016-03-12'::timestamptz) + '1 MONTH'::INTERVAL
      - DATE_TRUNC('month', '2016-03-12'::timestamptz) ;
------------------
 30 days 23:00:00

SELECT  DATE_TRUNC('month', '2016-03-12'::timestamp) + '1 MONTH'::INTERVAL
      - DATE_TRUNC('month', '2016-03-12'::timestamp) ;
----------
 31 days