code: func timeToJulianDay(t time.Time) int {
  
  	t = t.UTC()
  
  	month := int(t.Month())
  
  	a := (14 - month) / 12
  	y := t.Year() + 4800 - a
  	m := month + (12 * a) - 3
  
  	if t.Before(gregorianDate) { // Julian Calendar
  		return t.Day() + (153*m+2)/5 + 365*y + y/4 - 32083
  	}
  	// Gregorian Calendar
  	return t.Day() + (153*m+2)/5 + 365*y + y/4 - y/100 + y/400 - 32045
  }
docs: // timeToJulianDay returns the Julian Date Number of time's date components.
  // The algorithm is taken from https://en.wikipedia.org/wiki/Julian_day.