Answer by Firnas for Difference in months between two dates

You can have a function something like this.

For Example, from 2012/12/27 to 2012/12/29 becomes 3 days. Likewise, from 2012/12/15 to 2013/01/15 becomes 2 months, because up to 2013/01/14 it's 1 month. from 15th it's 2nd month started.

You can remove the "=" in the second if condition, if you do not want to include both days in the calculation. i.e, from 2012/12/15 to 2013/01/15 is 1 month.

public int GetMonths(DateTime startDate, DateTime endDate){    if (startDate > endDate)    {        throw new Exception("Start Date is greater than the End Date");    }    int months = ((endDate.Year * 12) + endDate.Month) - ((startDate.Year * 12) + startDate.Month);    if (endDate.Day >= startDate.Day)    {        months++;    }    return months;}