Does time start when you click on "Select Scenario", when you click on "Start", after the loading screen, when you click "we have to survive", or when you click on "OK" during the "Fight the Cold" popup?

Does time end when you click "OK" during the "The Storm Ends" popup, when the UI disappears, when "We Haven't Crossed the Line" appears, when "New London" appears, or when it returns to title screen?

click to get rid of the last message to gameplay begin, end when the final message appears.