How does a clock work?

Question

i was always curious how it worked.

how can it have an accurate sense of timing every tick of a second?

Answer 1

Clocks that plug into the wall have it easy - the power coming out of a wall outlet is 60Hz (60 pulses per second), and it's very tightly regulated by the power company.  All the clock needs to do is count the power pulses from the wall, divide by 60, and it will know the length of a second.  Unfortunately, if the power from the wall has noise signals on it, from faulty grounding or heavy appliances, it may lose count and the time may go off.

Battery powered clocks usually use a crystal oscillator to tell time.  A crystal, when cut to a certain size, will vibrate at a certain frequency in an electronic circuit.  However, the crystal may be a few microns too big or too small, so the clock may run a bit fast or slow.  

I have two clocks that run off wall power but have battery backups.  They keep good, identical time when the power is on, but in the event of a power failure, one gains 2 minutes per day and one gains 5 minutes per day.  After a power failure, they read different times, and must be manually synced up again.