;-------------------------------------------------------------
 
    FUNCTION WEEKDAY, Y, M, D, NWD, help=hlp
 
    IF (N_PARAMS(0) LT 3) or keyword_set(hlp) THEN BEGIN
      PRINT,' Compute weekday given year, month, day.'
      PRINT,' wd = weekday(y,m,d,[nwd])'
      PRINT,'   y, m, d = Year, month, day (Like 1988, 10, 31).      in'
      PRINT,'   wd = Returned name of weekday.                       out'
      PRINT,'   nwd = optional Weekday number.                       out'
      RETURN, -1
    ENDIF
 
    NAMES = ['','Sunday','Monday','Tuesday',$
         'Wednesday','Thursday','Friday','Saturday']
 
    NWD = ((YMD2JD(Y,M,D) + 1) MOD 7) + 1
    RETURN, NAMES(NWD)
 
    END