Did you leave the PSP on stand by or full OFF?
Remember that standby still uses up power, albeit a tiny amount, so perhaps your battery was flat... so the time would reset.... the information on your memory stick is independant to that of power in the unit so lack of juice would only effect the clock and without you adjusting the default settings the unit (when powered up) wouold seem only to have reset the clock.
Well that's my theory anyway
Des
:roll: