JD2Day:

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   Computes the day of the week from Julian day number.
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   Form:
   day = JD2Day( jD )
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   ------
   Inputs
   ------
   jD           (1,1) Julian date

   -------
   Outputs
   -------
   day          (1,3) 'Sun' 'Mon' 'Tue' 'Wed' 'Thu' 'Fri' 'Sat'

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Children:

Common: Math/R2P5
Common: Time/Date2JD