The DATETIME format in SQL servers is below:
YYYY-MM-DD hh:mm:ss
Below is an example:
2019-08-20
YYYY-MM-DD hh:mm:ss<--> 2019-08-20
DECLARE @date date = '12-21-16';
DECLARE @datetime datetime = @date;
SELECT @datetime AS '@datetime', @date AS '@date';
--Result
--@datetime @date
------------------------- ----------
--2016-12-21 00:00:00.000 2016-12-21