Answer by Konstantin Chernov for Difference in months between two dates

Here's how we approach this:

public static int MonthDiff(DateTime date1, DateTime date2){    if (date1.Month < date2.Month)    {        return (date2.Year - date1.Year) * 12 + date2.Month - date1.Month;    }    else    {        return (date2.Year - date1.Year - 1) * 12 + date2.Month - date1.Month + 12;    }}