system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How do electronics keep track of the time if they are turned off for a period of time and never connect to the internet?

For example if I have an iPad that I turn off for a couple days, and when I turn it back on while it has no internet access, how does it know what the time and date is?
gpt
Your iPad uses a small amount of its battery to keep the internal clock running, which is the only thing it's doing while it's shut down.

Laptops also do this, though sometimes it's through a small watch battery instead of the main battery.