The Very Mysterious Mystery of the Milk Cartons in NYC

I've wondered since becoming independent in New York City (and by extension purchasing milk on a regular basis) why there are two sell-by dates on milk cartons sold in the area. There is the standard sell-by date and then there is the NYC sell-by date, which is typically two to three days earlier than the standard sell-by date. Well, mystery solved. Not surprisingly, it has to do with city regulations on how long a grocer can sell milk after 6:00 a.m. on the day of pasteurization. Thank you, Gothamist, for enlightening me. I'm glad to see there are others curious about this (one of very, very many) New York City quirk.