code: def set(self, instance, value, **kw):
          
          if value:
              try:
                  value = DateTime(value)
              except SyntaxError:
                  logger.warn("Value '{}' is not a valid DateTime string"
                              .format(value))
                  return False
  
          self._set(instance, value, **kw)
docs: Converts the value into a DateTime object before setting.