Car Clock gone Haywire

The clock in our Highlander has suddenly started acting crazy. One day within an hour of parking the car, the clock was running 2 hours behind. Today, after being parked for 3 hrs, it was running 2.5 hrs fast.

Is this a short in the circuit or a problem with the battery?

There is probably a problem with the clock. If it is the battery, note the time just before you start the engine. Then start the engine. If the clock resets to 12:00, you probably have a battery problem, as the battery voltage is dropping too much from the load of the starter. If this isn’t the case, the clock is probably defective.

No, it’s not a short circuit.
Yes, it could be the battery. I’d test it or get it load tested.
Otherwise, it may just be that your clock is failing.

The clock has never reset to 12:00, and it only does it randomly. Not every day, or all the time.

Some clocks go to a random time when they lose power instead of resetting to 12am.

The problem is most likely with your clock. I seem to recall hearing or reading somewhere (maybe even here) that late model Highlanders have been having problems with defective clocks. It’s sort of ironic that the clock in a new Toyota can’t keep proper time, but the original analog Quartz clock in the dashboard of my '86 Chevy Silverado still keeps perfect time…