You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: PLENTY OF TIME 
Clue: A clock set in the year 2000 & losing 1 second a year would first be an hour off in this year
5600

Category: THE "SKY" IS FALLING 
Clue: America's first space station
skylab

Category: WHAT'S "UP"? 
Clue: Denver's victory over Green Bay in the Super Bowl was one of these

an upset