DECLARE @dt DATETIME
SELECT @dt = '12/21/2016 23:59:58:001'
SELECT FORMAT(@dt,'MM/dd/yyyy') -- returns 12/21/2016
SELECT FORMAT(@dt,'hh:mm:ss') -- returns 11:59:58
SELECT FORMAT(@dt,'HH:mm:ss') -- returns 23:59:58
SELECT FORMAT(GETDATE(),'HH:mm:ss.fff') -- returns 09:20:47.723, showing milliseconds