Date code (last four digits after DOT): the very last two is the year typically. The previous two is the week the tire was manufactured. For example, 3909 is on my General Altimax Arctic....they were made on the 39th week of 2009.
Tires should be no older than six years. As tires age (even if they are not even used), they get hard and can fail miserably.
http://pneusarabais.com has some 225/60-16 winters in the $85-$90 range. Entry level winter tires include Cooper Arctic Claw TXI. These are decent, but can be noisy when studded. I have had them on my Mazda truck for a couple of winters.
Also, look at the sidewalls of each used tire. Bulges mean that the cords have failed and should be avoided.
Dave
