This may sound a bit less relevant but I couldn't think of a better place to ask this question.
Now consider this situation, you install an OS on your system, set the timezone and time, do some stuff and turn it off. (Note that there is no power going in to the computer).
Now next time (say after some hours or days) you turn it on again, and you see the updated time.
How is this possible even when my computer is not connected to the internet and was consuming no power during the period it was down.(Is there some kind of hardware hack?)