Racing game timer and high score

Hi people ,
I am making a racing game and I have no idea how to implement a timer which will start when the vehicle will leave the starting_line trigger and stop when the vehicle enters the ending_line trigger and show it at the end game gui. Does anyone knows how to do it or knows where can i find the resources?

I would alo like to know how to implement a high score table for the best timings. Thank you very much.
billy