I ate a clock yesterday. It was so time-consuming.
Why this joke works
Consuming Time Literally
A time-consuming activity normally requires a long while to finish. Eating a clock makes the phrase literal because the meal itself consists of something that measures time. The absurd first sentence should be delivered without explanation, as though yesterday's menu was perfectly ordinary. Pause before the second sentence, then keep “time-consuming” together as one familiar expression. Listeners first hear a complaint about duration and then recognize that the speaker has supposedly consumed time in a much more direct way.
A closer look
The Object Becomes a Meal That Uses Up Its Subject
The first sentence reports an impossible snack with complete calm. “Time-consuming” normally means requiring a long duration, but eating a clock would literally consume a timekeeping object. “Yesterday” quietly strengthens the theme by locating the act in time. The short second sentence resembles a restaurant review, allowing the hyphenated adjective to deliver both the duration complaint and the physical consequence.
Fact behind the joke
A Clock Counts a Repeating Event
NIST explains that clocks measure intervals by counting regular physical events. A grandfather clock counts pendulum swings through gears, while a quartz clock divides a crystal vibration—often 32,768 hertz—into one-second ticks. The displayed time is information produced by that mechanism, not an edible substance stored inside it. Swallowing clock parts would create a medical emergency rather than a meaningful way to consume time.