SSIS date function

(DT_STR,4,1252)DATEPART( "yyyy" , DATEADD("year", -1, getdate())) + "-" +
RIGHT("0" + (DT_STR,4,1252)DATEPART( "mm" , getdate() ), 2) + "-" +
RIGHT("0" + (DT_STR,4,1252)DATEPART( "dd" , getdate() ), 2)

i am using the above function but this will not help me with leap year 

how to modify this