The build date (mm/yy) along with lots of other figures are printed on a white mylar label stuck to side of the driver door. It also shows separate GAWR (gross a? weight rating) for the front axle vs the rear. Other numbers I have yet to decipher.
Anyway, I had other info source: since mine was a factory order, which also allowed me track the build status codes thru their hotline in India. In May, I phoned them weekly to track progress using the status codes, and hoping that the crucial assemblies didn't happen on a
Monday or Friday 
. Although there nothing I could do about it.
It appeared that my Riot was not assembled on those 'lemon' days.
According to folklores, Mondays and Fridays are lemon days in many workplaces. Workers are not a their peak competences on those days, since workers drag themselves to work after a fun weekend: brain is stuck on 1st gear :zzz:. Similarly many workers (including pencil pushers) are on TGIF mode by Friday afternoon: brain is on overdrive to quickly wrap things up.

epper: