adding up millis

Using Arduino Programming Questions
4

CrossRoads:
If your math is all done in the form of

elapsedTime = (timeNow - timeEarlier); // add elaspedTime to add rideTime summary
where timeNow is the stopped time, and timeEarlier is the time you started

and all time related variable are unsigned long,
then there will not be a rollover problem.

Ah yes, I get it, that makes perfect sense... I was just over complicating it. Thanks!