def _offset_to_min(utc_offset):
    '''
    Helper function that converts the utc offset string into number of minutes
    offset. Input is in form "[+-]?HHMM". Example valid inputs are "+0500"
    "-0300" and "0800". These would return -300, 180, 480 respectively.
    '''
    match = re.match(r"^([+-])?(\d\d)(\d\d)$", utc_offset)
    if not match:
        raise SaltInvocationError("Invalid UTC offset")

    sign = -1 if match.group(1) == '-' else 1
    hours_offset = int(match.group(2))
    minutes_offset = int(match.group(3))
    total_offset = sign * (hours_offset * 60 + minutes_offset)
    return total_offset