Why does milk have different expiration dates in NYC?

Subject pretty much says it all, but for your out-of-towners - when you buy milk at a grocery store in New York City, it will have two expiration dates. Taking the carton I just finished off, it says

EXP April 04
IN NYC April 01

It’s April 2 and it’s still good, so what’s with the second date?

Bonus question - what is with the soda cans that have NEW YORK stamped on them? I generally only see it when I buy individual cans, not 12 packs.

A half-second Google search reveals wonders.