Master of time and space

Does anybody know how to start and stop a timer for a game where it starts after the menu scene and stops when going through a collider with a trigger.

Save the time when it started, and substract it from the time when you need to have this timer stopped.

var startTime : float= Time.time;

//later on:
var total : float= Time.time-startTime;
Debug.Log("it took"+total+" sec.ms");