A pun based on concepts of time, or using time diction. They are every bit as unbearable as regular puns. For example, this Cyanide & Happiness comic:
Shakespeare makes a number of chronopuns. Here’s the first I’ve found:
“And so from hour to hour we ripe and ripe,And then from hour to hour we rot and rot,And thereby hangs a tale.”—As You Like It, Act 2, Scene 7, Line 26-27.
In Early Modern English, “hour” and “whore” would have been pronounced identically. So we can measure our lives in hours, or in whores (as Jaques does), or, as Prufrock does, in coffee spoons.