May 15 2016?

That's the day you picked them up.

Old eggs only show a date...new eggs show a location too - so the old eggs don't show location.

EDIT I had dates thing wrong...

It's a bug. Even new eggs list this date, and the game wasn't released yet then.

Maybe some developer created a huge amount of eggs on May 15th during the development of the game, and Niantic is still distributing them on the Pokestops because the users still didn't hatch them all (Just kidding)

That's mean you are a time-traveler from the past or you got those eggs from another parallel universes.