Alright, in order to find out the date you look for the stepping and look for the four digits right after it.
For example (on my 2500 mobile):
I have an IQYHA0406UPMW. The stepping would be IQYHA and the date would be 0406. 0406 means 2004 (first two digits say '04'), and week '06.'
Hope that helps dude.