If property IsDayOfYearSpecified is true then property Begin and End should be interpreted as day of year instead of the specified date. For example 2012-03-01 is not the same day of year as 2013-03-01 since 2012 is leap year.

public bool IsDayOfYearSpecified { get; set; }

Public Property IsDayOfYearSpecified As Boolean
	Get
	Set

public:
property bool IsDayOfYearSpecified {
	bool get ();
	void set (bool value);
}

member IsDayOfYearSpecified : bool with get, set