UNITs of Payment

Jo, who was being tutored by Adric in hopes of someday achieving mathematical competence, if not excellence, asked why no one ever proofread dates mentioned in scripts.
The Brigadier agreed disgustedly. It was impossible to figure his pension payments based upon his years of work.
"Time is relative, old chap." said the 4th Doctor.
"It's my relatives I've got to support!" said the Brig. "Wife, two ex-wives, children, grandchildren......Now that I've got a new body, I'll have to go back to work! Goodby mandatory retirement age!"
"I know what you mean." said Davros. "They keep resurrecting me too!"