Resetting millis() and micros()
millis() and micros() overflow periodically. However, this is not a
problem: as long as you compare durations instead of
timestamps you can
forget about the overflows.

The liked answer also gives the trick for resetting millis(). Can be
handy for testing purposes, but you do not need this to handle the
millis() rollover problem. Notice that there is no clean way to reset
micros(): it relies on a static variable, i.e. a variable private to
the file defining it.