def calc_julian_days_dg(tlc_time):
    """Calculate the Julida dayys according to the fomula provided by
    DigitalGlobe. Found in section 4.1.2 
    here https://dg-cms-uploads-production.s3.amazonaws.com/uploads/document/file/207/Radiometric_Use_of_WorldView-3_v2.pdf

    Parameters
    ----------
    tlc_time: datetime.datetime

    Returns
    -------
    int:
        days since the beginning of the year -4712 
        Meuss, Jean. "Astronomical algorithms, 2nd Ed.." Richmond, VA: Willmann-Bell(1998). Pg 61
    """
    a = tlc_time.year // 100 
    b = 2 - a + (a // 4)
    UT = tlc_time.hour + tlc_time.minute/60 + \
        (tlc_time.second+tlc_time.microsecond)/3600
    jd = int(365.25*(tlc_time.year+4716)) + \
        int(30.6001*(tlc_time.month+1)) + \
        tlc_time.day + UT/24+b-1524.5
    return jd