Tires: mfg date on tires, dot code, z1

Question
I'm trying to find the mfg date on recently purchased tires, these are the numbers I've found which don't seem to have the info needed to get the date:  
DOT UYZ1, P-235/75R15-105S,
and R51037 which is follows an arrow within a circle

Answer
Ernie,

I've explained this in more detail here:

http://www.barrystiretech.com/dotcoding.html

Short version:

Look on the other side of the tire, because you've shown me a partial DOT code (UY Z1) and that is allowed for one side, but not the other.