Ignore NULL Argument In SELECT

I have a stored procedure which accepts 3 arguments that are used in the WHERE clause of a SELECT Statement

CREATE PROCEDURE [dbo].[MyProcedure] @argYear INT, @argMonth INT, @argDay INT

AS

SELECT *

FROM MyData

WHERE
MyData.Year = @argYear AND MyData.Month = @argMonth AND MyData.Day = @argDay


The problem that I am having is @argDay is an "optional" argument. If @argDay is NULL then I want to basically ignore the "AND MyData.Day = @argDay" condition.

Is there an easier way to do this than:

IF @argDay is NULL

SELECT *


FROM MyData


WHERE

MyData.Year = @argYear AND MyData.Month = @argMonthELSE

SELECT *


FROM MyData


WHERE

MyData.Year = @argYear AND MyData.Month = @argMonth AND MyData.Day = @argDay

END IF

Thanks