You don't need to format anything! Date should be a date, not string!
If you want to insert data into SQL database, you should know the format which is used by MS SQL server. Have a look at
SET DATEFORMAT[
^] command.
Finally, you should use
stored procedure[
^]:
USE DataBaseName;
CREATE PROCEDURE InsertMyData
@myDate DATETIME
AS
BEGIN
SET DATEFROMAT dmy;
INSERT INTO TableName (DateField)
VALUES(@myDate)
END