Function            dayofweek - find the day of the week

  Syntax              int dayofweek(double jul);

  Prototype in        datehk.h

  Remarks             finds the day of the week for a given Julian
                      (Type E) date

  Return value        returns 0-6 (Sun...Sat)

  See also            Appendix A
                      datehk.h

  Example             see demodate.c