Date code is irrelevant, guide at best. Engine number is the important thing. Date codes are normally in the month(s) preceding the engine number, often the same month. Can be many months prior to build date though and consecutive PSN's on vehicles can have engines 1000's of numbers apart.

HZ is a Sandman, HX is almost certainly but you can't 100% tell from the ID plates like you can with the HZ.