Why doesn't my clock keep the correct time?

Why doesn't my clock keep the correct time?
When the power goes out, or when clock is unplugged while moving its location, the clock does not keep the correct time.

ANSWERS:

"When moving your clock or unplugging it from the wall it goes into back up power mode with the back up battery, thus it resets the time. Its possible that your back up battery may be dead if it automatically does not keep time, here is a link to the back up battery replacement guide.

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