The only date stamps you will find on XM193, is on the shell casings. All that tells you, is what year the casing was made. It has nothing to do with when the ammo was made. I have opened 20 round boxes of XM, and seen 3 different years in the same box. The only issues I have heard of with boxed XM, is case mouth, or primer sealant. Some lots are sealed better than others.
Your best bet would be trying to find lot numbers which may have had issues. I personally have never had problems with boxed XM. The PD variety, is another story. It is the bulk packed stuff. The rounds are loose in a plastic bag, inside a cardboard box. I have had some with split, and dented cases, little or no powder, and bullets seated loose in the necks.