docs: public static long addMonths(long timestamp, int m) {
  		final long millis =
  			DateTimeUtils.floorMod(timestamp, DateTimeUtils.MILLIS_PER_DAY);
  		timestamp -= millis;
  		final long x =
  			addMonths((int) (timestamp / DateTimeUtils.MILLIS_PER_DAY), m);
  		return x * DateTimeUtils.MILLIS_PER_DAY + millis;
  	}