def jd(date = self)
      y30 = (date.year / 30.0).floor
      day_number = 1948084 + y30 * 10631 + day_of_year(date)

      if date.year % 30 == 0
        day_number
      else
        day_number + DAYS_IN_30_YEARS[date.year - y30 * 30 - 1]
      end
    end
def jd(date = self)
      y30 = (date.year / 30.0).floor
      day_number = 1948084 + y30 * 10631 + day_of_year(date)

      if date.year % 30 == 0
        day_number
      else
        day_number + DAYS_IN_30_YEARS[date.year - y30 * 30 - 1]
      end
    end
return Julian Day number associated with this (or specified) Hijri date