For anyone that would like to do their own testing, here's the test table I've been using for all of this...

WITH cteRandomDT AS

(

SELECT TOP 1000000

DateTimeDT = RAND(CHECKSUM(NEWID())) * DATEDIFF(dd,'2000','2020') + CAST('2000' AS DATETIME)

FROM sys.all_columns ac1

CROSS JOIN sys.all_columns ac2

)

SELECT DateTimeDT

,DateTime2DT = CAST(DateTimeDT AS DATETIME2(3))

INTO #JBMTest

FROM cteRandomDT

;