If you get back together after a break up...

Do you continue to count the years together since the 1st moment you started dating or do you start all over again. 
My niece was with a man for about 4-5yrs they broke it off for about 3years, they both moved on, reconnected and dumped whoever they were with and got back together. They had a child and then got married. If you ask them how long they have been together they will say over 10yrs. But how? If you were apart for some time and even was in different relationships....
How do you guys feel? The clock never stops? Or you should push the restart button?