Three dinners in one day
The puzzle
A man ate dinner three times in one day.
He is not a big eater, and all three were ordinary portions.
See the answer (spoiler)
Spoilers from here on. If you want to work it out yourself, leave this folded and move on.
Answer
He flew across several time zones.
He had dinner before leaving, dinner was served on the plane, and by the time he landed it was dinner time again.