The date that the meat was cryovaced should be listed on the outside of the cardboard case it comes out of. I have seen this on cases of IBP and EXEL ribs. I ask the person handling the meat if they can find it for me and they usually have no problem unless the case was thrown out.
I recently heard someone talking about aging briskets for 30 days in the fridge while still in the cryovac at 34 degrees before he cooks them for comps. He also said that you could age them to 30 days and then freeze them until you are ready for them as well.