Add dates in SQL Server using DATEADD function

i accomplish is below way 

DECLARE @InvoiceDate Date = '2021-02-15'
DECLARE @ContractStartDate Date = '01-03-2021'
DECLARE @ContractEndDate Date = '01-03-2024'
SELECT DATEADD(DD, DATEDIFF(DD, @ContractStartDate, @ContractEndDate), @InvoiceDate) AS Finaldate;