Tire age when purchase new

So I just bought a set of new tires from Tire Rack last month and I just noticed yesterday that the birthday of the tires according to DOT # is 0413. That means the 4th week of 2013. So it is one and half year old....:tomato:
Is this acceptable? I haven't had the tires mounted yet. Should I make an exchange?? What do you all think?

Thanks