The lastDayOfMonthCalculation global property controls special handling of the last day of a month in calendar date calculations. When set to YES (the default), adding or subtracting a whole number of months, quarters, or years from a date that is the last day of a month will always result in a date that is the last day of the resulting month. If set to NO the result will keep the same day of the month if it exists in the resulting month, or will wrap around to the 1st, 2nd, or 3rd day of the following month depending on the difference in month lengths.