In

select @dt = start

from openxml ( @idoc, '/root', 1 )

with ( start datetime2 'start' )

Try changing the DATETIME2 portion to DATETIME2(0) to see if keeping the data type consistent helps.

OR In this case since you have the zone where the time is maybe try substituting datetime2 with DATETIMEOFFSET in the code , then in your select cast this to SMALLDATETIME. See if this helps you.