public void SubstractMonth(int m) { if (m < 0) { AddMonth(-m); } else { if (clock == null) { setClock(); } Month[] monthList = clock.getMonthList(); int newMonth = month.Month_number - m; if (newMonth >= 0) { month = monthList[newMonth]; } else { while (newMonth < 0) { newMonth += monthList.Length; if (yearMatters) { SubstractYear(1); } } } } }