Answer by Simon Mourier for Difference in months between two dates

Here is a simple solution that works at least for me. It's probably not the fastest though because it uses the cool DateTime's AddMonth feature in a loop:

public static int GetMonthsDiff(DateTime start, DateTime end){    if (start > end)        return GetMonthsDiff(end, start);    int months = 0;    do    {        start = start.AddMonths(1);        if (start > end)            return months;        months++;    }    while (true);}