Dave
Tires have had to have a DOT code since the early seventies. On whitesidewall tires the code will be on the blackwall side. Your concern will be the last three numbers as they indicate the month and year of manufacture. i.e a tire manufactured this week would have a date code of 507. Remember this rolls over each ten years. The other letters and numbers indicate manufacturer, plant location, etc.
HTH
Mike C (tire salesman)