Did it expire in May 2017 or does it say "Best if Used by May 2017"?

Food won't expire that quickly---unless it's fresh foods like meat, dairy and produce. The dates stamped on foods are there to make you "think" you mut use it fast or throw it away. The food industry depends on customers always buying. So they can keep on alwasy priducing. To encourage a constant turn over on your pantry shelve they stamp dates on foods to encourage to throw away the old--so you buy the new. But it's rarely if ever "bad" when you do.

Food doesn't "expire" on some predetermined date. It's just better quality prior to that date. As for peanut butter, it will eventually become rancid, but it's not unsafe to eat at that point. Just very unpleasant to eat.

Yes

No

Cans or jars are good for one year after the expiration date if they have not been opened.

Peanut Butter wouldn’t ever be expired in this house.