In case of uncertainty (times not specified), we assume that we are in a valid range.

def _after_valid_time_range(self):
        """
        In case of uncertainty (times not specified), we assume that we are in a valid range.
        """
        if self.end_time is not None:
            try:
                if self.time > self.end_time:
                    return True
            except TypeError:
                return False
        return False