End of the year mileage? I used two different cars, borrowed one for rideshare. Does end of the year mean when I stopped using this car for rideshare & regular work?

I am referring to the car I borrowed before I bought a new car. With the borrowed car, I used it for rideshare and regular work commute. I stopped using it completely when I bought a new car. So does end of the year mileage mean at that point I stopped using it or the actual mileage at the end of the calendar year even if I stopped using it well before the end of the calendar year?