Note: This is a simple way to create a Global timer behavior to use in your AC game.
You can create a Global integer Variable to store the number of e.g. seconds that have passed since your game begins.
Create a new ActionList that's set to Run In Background, and have it run a Variable: Set Action to increase the integer's value by 1, then use an Engine: Wait Action to wait 1 second, then connect this action back to the first Action (to create a loop). If you then assign this as your ActionList on start game (in the Settings Manager), it'll track how many seconds have passed, which you can use to calculate the time.
-Original tip was provided by ChrisIceBox. Edited by Alverik-