@Edent fun question of how your totp device knows the time. If you've gone back before the 70s there isn't GPS to sync to. If the totp device doesn't know it's time travelling then it's clock probably still thinks its minutes after it left. Hope all of you jumped at the same time. If you jump back to the same time you left, you now get clock drift errors as you've accumulated the time you spent in the past and your clock thinks it's in the future. Of course if you've invented a time machine you can probably make a clock that understands that it's been time travelled.