create procedure lib_date_leap_year (
                     ofyear smallint)
                   returns (
                     is_leap_year smallint)
  as
    begin
      /*
        check year for leap year
          is_leap_year : 0 = false
                         1 = true
      */

      if (ofyear is null)
        then
          is_leap_year = null;
        else
          if (  extract( yearday from cast( ofyear || '-3-1' as date))
              < 60)
            then
              is_leap_year = 0;
            else
              is_leap_year = 1;

      suspend;
    end