system
Given the following post, respond as if you're commenting on Reddit:
human
Why do some digital clocks lose or gain time? My coffee maker has to be readjusted every couple months to fix the time. Used to have a car that would gain a few minutes each month.
gpt
This has to do with the crystal that is used in the circuit, as well as other components in the circuit as well.

Every digital clock uses a crystal. When a current runs through the crystal, it vibrates at a distinct, constant frequency. The rest of the circuit uses that frequency to and does a ratio "This many vibrations is equal to one second"

Well, most cheap digital clocks arent as close to perfect as the atomic clock, which we hold to be the true time. 

The crystal in your digital clocks may vibrate (made up numbers) 1000 times per second... But maybe sometimes they vibrate 1003 times per second, or 995 times per second.
There are tolerances like this to just about every single part in circuitry (maybe a resistor that is supposed to be 1000 ohms is actually 999.5 ohms, but it's within the acceptable range for manufacturers that buy them in bulk)

These tolerances are what will slowly throw off the time in your clock.

Another tolerance issue could be the part of the circuit that counts the frequency. Or perhaps the people that designed the circuit were slightly off in their math.

It can be all of these things.