You can schedule content to play at different times of the day or different days of the week.
In order to support scheduling (day parting), the unit either needs a real time clock or needs to be connected to a network with a time server to set the date and time. You can also manually set this clock for any players not connected to the network.
All currently shipping players have a real time clock.
For legacy players, the HD120 and HD810 have a real time clock. These units are non network units.
The HD210w, HD1010, HD1010w, HD220, HD1020, XD230, XD1030 and XD1230 have networking and a real time clock.
The HD210 units manufactured since November 2010 have a real time clock. These units have a reset button next to the GPIO12 button, and they also have the letter F as the 3rd digit in the serial number. Any earlier HD210s would require a network with a time server to set and maintain the time. This also applies to the HD110 and HD410.