How to know when my iPad is made

You can use this link. Go to Settings > About to get your Serial Number and type that into the bar in this link:

http://www.chipmunk.nl/cgi-fast/applemodel.cgi

You can also tell by just reading the serial no.

The first 2 digits indicate the factory (DM, DN etc).

The 4th and 5th digits are the build week.

So..

DMx13xxxxx would mean DM factory and build week 13.