I once went to Target to return some potato chips that were twelve months out of date.
Fortunately, I had the receipt from a few days before but I still got the impression that the customer service slave thought I was pulling a fast one.
It was a multipack and the outside only had the month and day. It wasn't until I took out an individual pack that I realized they actually meant LAST November.
It wasn't so much about getting that cash back as getting the nasty stale product off the shelf. I ate one before I realized they were out of date and it was quite foul.