I wouldn’t want the secret service to be after you for asking this question. However as a non lawyer, any president’s term ends on January 20 of the fourth year after the last scheduled inauguration. I suppose Congress can authorize another presidential election since only Congress has the power to set the date when electors vote for President.
I haven’t been physically inside the USA for several years. I don’t even have a current US passport. If the SS wants to fly out here to question me, I think they must have too much time on their hands.