code: public static long toMJD(GregorianDate date) {
  
          return GregorianMath.toMJD(date.getYear(), date.getMonth(), date.getDayOfMonth());
  
      }
docs: /*[deutsch]
  <p>Ermittelt das modifizierte julianische Datum. </p>
  
  @param   date    gregorian date
  @return  days since [1858-11-17] (modified Julian date)
  @throws  IllegalArgumentException if the argument is out of range
  @see     #toMJD(int, int, int)