T-SQL UNIX timestamp function

fn_GetUnixTimestamp.sql

/* Create function */
CREATE FUNCTION [dbo].[fn_GetUnixTimestamp]
(
  @CT DATETIME
)
RETURNS BIGINT
AS
BEGIN
  DECLARE @CTS BIGINT
  SELECT @CTS = (CAST(DATEDIFF(second, '1970-01-01', CAST(GetUtcDate() AS date)) AS bigint)*1000)
				+ DATEDIFF(ms, CAST(GetUtcDate() AS date), GetUtcDate()) 
  RETURN @CTS
END

/* Usage */
SELECT [dbo].[fn_GetUnixTimestamp](GetUtcDate())