Usually the date of manufacture is part of the DOT code:
Quoted from another site:
The tire may contain a D.O.T. number. The last three digits show the year and week that the tire was manufactured. e.g., a tire stamped 324 means the tire was made in the 32nd week of 1994. Hopefully, it will not be too difficult to tell the difference in a tire made in 1984 from one made in 1994.
So I don't know what the 1993 represents.
