select 
  to_char(
    generate_series( 
        date( cast( to_char(current_date, 'YYYY' ) as integer)     || '-02-01' )
      , date( cast( to_char(current_date, 'YYYY' ) as integer) + 1 || '-01-01' )
      , interval '1 month'
    ) - interval '1 day', 'DD')
;

 to_char 
---------
 31
 28
 31
 30
 31
 30
 31
 31
 30
 31
 30
 31
(12 rows)