Answer by Morgs for Difference in months between two dates

Here is my contribution to get difference in Months that I've found to be accurate:

namespace System{     public static class DateTimeExtensions     {         public static Int32 DiffMonths( this DateTime start, DateTime end )         {             Int32 months = 0;             DateTime tmp = start;             while ( tmp < end )             {                 months++;                 tmp = tmp.AddMonths( 1 );             }             return months;        }    }}

Usage:

Int32 months = DateTime.Now.DiffMonths( DateTime.Now.AddYears( 5 ) );

You can create another method called DiffYears and apply exactly the same logic as above and AddYears instead of AddMonths in the while loop.