def __from_format(jd: float, fmt: str) -> (int, float):
    """
    Converts a Julian Day format into the "standard" Julian
    day format.
    Parameters
    ----------
    jd
    fmt

    Returns
    -------
    (jd, fractional): (int, float)
         A tuple representing a Julian day.  The first number is the
         Julian Day Number, and the second is the fractional component of the
         day.  A fractional component of 0.5 represents noon.  Therefore
         the standard julian day would be (jd + fractional + 0.5)
    """
    if fmt.lower() == 'jd':
        # If jd has a fractional component of 0, then we are 12 hours into
        # the day
        return math.floor(jd + 0.5), jd + 0.5 - math.floor(jd + 0.5)
    elif fmt.lower() == 'mjd':
        return __from_format(jd + 2400000.5, 'jd')
    elif fmt.lower() == 'rjd':
        return __from_format(jd + 2400000, 'jd')
    else:
        raise ValueError('Invalid Format')