Clock synchronization between 2 controllers

I am reading data from a microcontroller at 10ms sampling time. The problem is that the data is not exactly 10ms due to the drift in the crystal oscillator of the controller. Hence over time I notice that the outputs vary significantly because of this drift. I am trying to build a time synchronization module, where I periodically(every 1sec) sync the processor clock with a reference clock(ideal clock). Every 1 second, I calculate the slope of the actual clock vs the original clock and apply that value to the next period (1sec). However even with this periodic slope correction, it does not solve my time synchronization problem. Any thoughts or ideas about how to synchronize the clocks in a better and efficient way?

time_sensor_x = time_sensor(1) : 0.01 : length(time_sensor)/100;  %i"time_sensor_x" is the ideal clock, "time_sensor" is the actual clock.

%-----Slope calculation------%
k = 1;
for i = 1:100:length(time_sensor_x)
    slope_value(k) = time_sensor(i)/time_sensor_x(i);
    k = k+1;
    t = i;
end

%-----Slope correction and new time calculation------%

k = 1;
for i = 1:length(time_sensor_x)
    time_sensor_corrected(i) = (1/slope_value(k))*(time_sensor(i)); %corrected time
    if mod(i,100) == 0
        k = k+1;
    end
end