Tires: date codes on Assurance comfort tread, 4 digits, tire size

Question
I thought I knew how to read the date codes, but find I am a dummy this time.
I just had four of the above put on our 03 limited (Buick) and cannot read the coding.
It reads; [DOT ][M6M3]  [18HR][   ](nothing in the last rectangle).
Can you help me on this?
Thanks,
Ken Mc

Answer
Ken,

Yup, I can help.  Look on the other side.  The date code only has to appear on one 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.