code: def to_daydate(cls, *argv):
          
          argc = len(argv)
          if argc == 3:
              year, month, day = argv
          elif argc == 1:
              dval = argv[0]
              try:
                  year = dval.year
                  month = dval.month
                  day = dval.day
              except AttributeError:
                  raise InterfaceError("Unsupported python date input: %s (%s)" % (str(dval), dval.__class__))
          else:
              raise InterfaceError("Date.to_datetime does not support %d arguments." % argc)
  
          TURN_OF_ERAS = 1721424
  
          if month < 3:
              year -= 1
              month += 12
  
          if ((year > 1582) or
                  (year == 1582 and month > 10) or
                  (year == 1582 and month == 10 and day >= 15)):
              A = int(year / 100)
              B = int(A / 4)
              C = 2 - A + B
          else:
              C = 0
  
          E = int(365.25 * (year + 4716))
          F = int(30.6001 * (month + 1))
          Z = C + day + E + F - 1524
          return Z + 1 - TURN_OF_ERAS
docs: Convert date to Julian day (DAYDATE)