A few thoughts:
If one is going to be fussy about the manufacture date, then one ought to state that up front. It's OK to be fussy, but it's not OK to be fussy without warning the sales guy.
Tires in storage age very slowly compared to tires in service.
It is common in the tire industry to believe that any tire within 6 years of its manufacturer date can be sold as new. I said "Believe" because I know of no data that supports that statement - HOWEVER - the company I worked for could not find any significant difference between freshly made tires and tires stored in their warehouse for 3 years.
Heat seems to be the largest contributor to tires aging. Tires operating in Arizona age way faster than tires in colder climates. See the Arrhenius rule that says that the rate of a chemical reaction doubles for every 10°C increase in temperature.
My take on the various (and contradictory) statements about tire aging is that 6 years is the limit if you live in a hot climate (AZ, NV, CA, TX, and FL), and if you live in a cold climate (MN, ID, ND, WI, or MT) than the limit is 10 years. Since this is a Canadian website, I'm thinking that 10 years applies.