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)
##</code><code>##

select to_char(generate_series('20140201','20150101',interval'1mon')-interval'1','DD');
##</code><code>##

select to_char(generate_series('140201','150101',interval'1mon')-interval'1','DD');  -- Pg (9.5dev)
SELECT TO_CHAR(ADD_MONTHS(DATE'14-1-1',LEVEL)-1,'DD')FROM Dual CONNECT BY LEVEL<13;  -- Oracle (10g)
SELECT TO_CHAR(TO_DATE(LEVEL,'MM')-1,'DD')FROM Dual CONNECT BY LEVEL<13;

select to_char(to_date(generate_series(2,13)::text,'MM')+interval'1y -1s','DD');  -- Pg. awful but works :)

SELECT TO_CHAR(LAST_DAY(TO_DATE(LEVEL,'MM')),'DD')FROM Dual CONNECT BY LEVEL<13;  -- Oracle. "saved 3 char'
SELECT TO_CHAR(TO_DATE(LEVEL,'MM')-1,'DD')FROM Dual CONNECT BY LEVEL<13;          -- Oracle. "start from december" (shortest)

select 30+(3+(3*m+3)%5-(3*m+1)%5)/5from generate_series(3,13)f(m);  -- wrog's (short but incomplete: march through january)