// No of years * 12 + no of months + (-1) if startday is greater than endDay
private static int monthDifference(DateTime startDate, DateTime endDate)
{

int monthsApart = 12 * (endDate.Year - startDate.Year) +

endDate.Month - startDate.Month + ((startDate.Day - endDate.Day > 0) ? -1 : 0);

return monthsApart;

}