Returns a new DateTime that adds the specified number of years to the value of this instance.
An object whose value is the sum of the date and time represented by this instance and the number of years represented by value.
Type Reason ArgumentOutOfRangeException The resulting DateTime is less than DateTime.MinValue or greater than DateTime.MaxValue.
If the current instance represents the leap day in a leap year, the return value depends on the target date:
If value + DateTime.Year is also a leap year, the return value represents the leap day in that year. For example, if four years is added to February 29, 2012, the date returned is February 29, 2016.
If value + DateTime.Year is not a leap year, the return value represents the day before the leap day in that year. For example, if one year is added to February 29, 2012, the date returned is February 28, 2013.
The following example illustrates using the DateTime.AddYears(int) method with a DateTime value that represents a leap year day. It displays the date for the fifteen years prior to and the fifteen years that follow February 29, 2000.
code reference: System.DateTime.AddYears#1