Solved, if placing jcalendar on main custom dialog it correctly numbering, if placing on other form you must try to change month by your hand and then jcalendar will do correct number. -> SOLUTION just make new form, set form color into default, place jcalendar, anchor center, just call on every form it will do correct date numbering. It will be beautiful if we do transition on touching button -> jcalendar form open -> do transition.