Two batteries or phantom power?

I have three Sansa Clip+. Their date and time is accurate despite being off for long periods of time. Does the clock use its own battery such as a clock battery? Or does the clock use phantom power from the main battery?

It does not make sense for the MP3 player to have a clock in which users have to go to settings > system settings > date and time to see the date and time. Is the date and time used for some other purpose?

Date and time are also used for “security”–that is, nasty crippling restrictions–in  DRM (digital rights misery) files, like library audiobooks or music subscription services.

Even when you battery is drained, it still has power on it and that’s what the clock uses. Just like your phone. The clock resets if you take off the battery.