Hi — It depends how accurate you want to get because the solution proposed by RenatoB would be simple to implement but will suffer from some rounding down problems. If, for example, you run for 1.9 second only the first second would have been registered. For more accuracy you could grab the exact time at the beginning and end of each run session and subtract one from the other to calculate duration and add this number to a variable that keeps a running total for you.