beer clock

The level of beer in the last pitcher or glass, that determines when it's time to leave the bar or restaurant. i.e., when it's empty it's time to go -- and not before. (Obviously the beer clock can be reset by ordering another pitcher/glass.)

Child: Dad when are we going to go?
Dad: When the beer clock says so (pointing at the pitcher that isn't empty)!

Beer Clock

You tell time by the amount of beers consumed. Everyone has a different "schedule".

"Hey. What time is it?" Joe asked groggily.

"Umm..." Max peered at the number of empty beer bottles in front of him. "I'd say about 2:30 AM."

"Whoa! How do you know?" Joe asked with wide eyes.

"Beer clock." Max replied knowingly, then promptly fell asleep.