To prevent the unauthorized utilization of contents with a time limit.

When the contents with the time limit stored in a personal computer or the like are stored in the flash memory 80 of a portable device 6, time information T at the point of time is stored together as well. The time information T is also stored in an RTC 87 and the RTC 87 continuously updates the time information T with the time information T as a reference. The time information T updated by the RTC 87 is subscribed in the flash memory 80 as well at a prescribed timing. In the case that power supply from a dry cell 61 is temporarily stopped and the supply is restarted, the time information T stored in the flash memory 80 is supplied to the RTC 87 and the updating of the time information T is newly started with the supplied time information T as the reference. The time information T is used for managing the contents with the time limit.