def hmsm_to_days(hour=0, _min=0, sec=0, micro=0):
    """Convert hours, minutes, seconds, and microseconds to fractional days.
    --------
    Examples
    --------
    >>> hmsm_to_days(hour=6)
    0.25
    --------
    :param hour: Hour number. Defaults to 0. (int)
    :param min: Minute: number. Defaults to 0. (int)
    :param sec: Second number. Defaults to 0. (int)
    :param micro: Microsecond number. Defaults to 0. (int)
    :returns: Fractional days. (float)
    """
    days = sec + micro / 1000000.0
    days = _min + days / 60.0
    days = hour + days / 60.0
    return days / 24.0
