jd2dow.py

import math

def jd2dow(jd):
#% JD2DOW  Converts Julian date to day of week (Sun=1,...,Sat=7)
#%   Adapted from the algorithm from "Practical Astronomy with
#%   Your Calculator" (Third Edition) by Peter Duffett-Smith,
#%   Cambridge Univeristy Press, 1988. Non-vectorized version.
#%   See also CAL2JD, DOY2JD, GPS2JD, JD2CAL, JD2DOY, JD2GPS,
#%   JD2YR, YR2JD.
#% Version: 24 Apr 99
#% Usage:   dow=jd2dow(jd)
#% Input:   jd  - Julian date
#% Output:  dow - day of week (1=Sun,...,7=Sat)

#% Copyright (c) 2011, Michael R. Craymer
#% All rights reserved.
#% Email: mike@craymer.com

    dow = -1

    if jd < 0:
        print('Julian date must be greater than or equal to zero')
        return dow

    dow = math.floor(numpy.remainder(jd+1.5,7))+1

    return dow