A method for counting a service duration of time measurement on a clock signal including periodic transitions and for determining an actual duration (tmr) of measurement as a function of the service duration, the signal having undergone spectrum spreading according to a periodic variation algorithm causing a frequency modulation of the clock transitions of the signal and creating a difference between actual duration (tmr) and service duration. There are counted during successive time increments at least service times for starting (t_d_s) and stopping (t_a_s) and, on the basis of these times, there are determined actual times for starting and for stopping (t_d, t_a) serving for the calculation of the actual duration of measurement (tmr) as a function of the parameters of the variation algorithm. The invention also relates to a method of continuous compensation of the error between actual and service durations.