def parsable_date_validator(input_str):
    """
    A filter allowing any string which can be parsed
    by dateutil.
    Raises ValidationError otherwise.
    """
    try:
        get_time_from_str(input_str)
        return input_str
    except ValueError:
        raise ValidationError(
            f'Expected format: {DATE_INPUT_DESCRIPTION}. '
            '(Ctrl-C to exit)\n'
        )

    A filter allowing any string which can be parsed
    by dateutil.
    Raises ValidationError otherwise.
    
gcalcli/validators.py