Anyone know how to determine the "Date of Manufacture" of a Dell Laptop Battery?

 

I cannot find a "plain English" date anywhere on this battery so it must be coded into some of the numbers.

 

 

The battery in question:

   Dell (branded with Dell logo)

   Rechargeable Li-ion Battery

   Rating: 14.4V 2500 mAh, 2A

   Make in Japan

   Model name: Li-ion 36

   Dell P/N 15622

 

The bar-code label says:

   12792-6BM-BZN3

 

DP/N 00015622  Rev A00

 

Problem:

This battery was purchased as "new" but it appears to be dead and will not take a charge. It has a test button on the battery with 5 indicator lights but none of them light when the button is pressed. It's been charged for 10 hours and still no life.

 

TIA

Blue57