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 built-in way in Postgres to do that?

Answer 1

SELECT  
    DATE_PART('days', 
        DATE_TRUNC('month', NOW()) 
        + '1 MONTH'::INTERVAL 
        - '1 DAY'::INTERVAL
    )

Substitute NOW() with any other date.