Description
int 
cal_to_jd ( int calendar, int month, int day, int year)
     cal_to_jd() calculates the Julian day count
     for a date in the specified calendar.
     Supported calendars are
     CAL_GREGORIAN,
     CAL_JULIAN,
     CAL_JEWISH and
     CAL_FRENCH.
    
     See also cal_to_jd().