Tires: Goodyear missing DOT code, goodyear assurance tripletred, goodyear assurance tripletred tires

Question
I just had 4 new Goodyear Assurance TripleTred tires put on by my local garage. When checking for the DOT numbers I found that two were missing the last 4 digits indicating the month / year of manufacture. Two had the "normal combination" of DOT followed by 4 letters /4 letters and 4 digits. But the other two were missing the four digits at the end. Should I be concerned about this?
Thanks for your help,
Peter

Answer
Peter,

The date code only has to appear on one side, so look on the other side.

DOT codes are a 10 to 12 digit number located near the letters "DOT".  BTW the digits can be numbers or letters.

The first 2 digits are a code for the manufacturing plant.  

The next 2 digits are a code for the tire size.  

The next 3 or 4 digits are a code for the type of tire.  

The last 3 or 4 digits are the date code.  The format is week/week/year/year or week/week/year.  

Starting in the year 2000, the date coding used is 4 digits.  That means the highest number you should see for the year is 08.  Before 1999 the format was 3 digits.  1999 and 2000 are transition years, so you will find both 3 and 4 digits.