If law enforcement wants to bypass this, the obvious approach would be to just remove the battery (to remove power from any internal RTC chip) and put the device in a Faraday cage (to block external time signals like GPS and the cell network). Then the shutdown clock would literally stop ticking until they turn it on again.
Sure, this might not stop the NSA of FBI, but if it limits the threat vector to 3 letter agencies, it is still a win.
Police departments use Faraday bags to isolate the communications of a device once they take it into custody. I assume they do this to prevent RemoteWipe() commands from running from external entities to preserve evidence.
Might this constitute 'tampering with evidence'?
that it needs a trusted measurement of the current time.
So you test ~7days runtime or external clock says you've gone > 7days. Lock on either condition. You can mess with the latter as you say, but not the former. Well I suppose you can de-power the device but that doesn't really help you either. Am I missing something?
so perhaps the only point of this "band-aid fix" is that if the user hasn't connected his iPhone to his computer for 7 days (i'm guessing most non-tech people rarely connect their phones to their computer), the chances are greatly increased that the lightning port is already disabled once it's captured by law enforcement/whoever.
“To improve security, for a locked iOS device to communicate with USB accessories you must connect an accessory via lightning connector to the device while unlocked – or enter your device passcode while connected – at least once a week.”
Because the quote says "enter your device passcode while connected"
= the device has to be connected while entering the pin.