Calculate the number of months between two dates with C#

Say you’d like to calculate the difference between two dates in terms of number of months.

The following simple function will do just that: return the absolute number of months between two dates:

public static int GetMonthDifference(DateTime startDate, DateTime endDate)
{
	int monthsApart = 12 * (startDate.Year - endDate.Year) + startDate.Month - endDate.Month;
	return Math.Abs(monthsApart);
}

Usage:

DateTime now = DateTime.UtcNow;
DateTime past = now.AddMonths(-13);
int monthDiff = GetMonthDifference(now, past);

monthDiff will be 13 as expected, i.e. not -13.

View all various C# language feature related posts here.