My router RB751U-2HnD keep files from external usb disk after reboot. Power lost.
Plase look for (Creation time) files. I have ntp client active.
Yesterday files are with and with today. Year 1970 where from there?
when the router reboot the time = 1970 after internet connection is available the ntp will update..
that is what i notice…
Yesterdey before reboot date was corectly.
cause ntp has already resync the time..
u try power off and power on with out internet see if the time sticks or not 
My router RB751U-2HnD keep files from external usb disk after reboot. Power lost.