Many thanks to The WordPress Math Blog Voducdien for posting this wonderfully simple, yet challenging problem. They tell it so well, I am just going to quote them:
A manager asks his subordinates to leave for lunch between 12 p.m. and 1 p.m. and come back between 1 p.m. and 2 p.m. with the condition that when they leave and come back the hour and minute hands swap their places exactly. What time do they have to leave and come back?
I know what I got.
What did you get? Post it in the comments. (Of course, you need to explain your reasoning…)