Just for interest's sake, here's the in-line function written to use SQL Server 2012:

CREATE FUNCTION dbo.agent_datetime_inline

(

@Date integer,

@Time integer

)

RETURNS TABLE WITH SCHEMABINDING

AS RETURN

SELECT

DATETIMEFROMPARTS

(

@Date / 10000,

@Date / 100 % 100,

@Date % 100,

@Time / 10000,

@Time / 100 % 100,

@Time % 100,

0

) AS date_time

Test results using Jeff's rig:

Michael's code: 1155ms

New function: 670ms