Traincascade time measurement is going loco (Bug #3656)

If you look at the cascadeclassifier.cpp, I submitted a piece of code to measure the time for each stage to train.

// Output training time up till now
float seconds = float( clock () - begin_time ) / CLOCKS_PER_SEC;
int days = int(seconds) / 60 / 60 / 24;
int hours = (int(seconds) / 60 / 60) % 24;
int minutes = (int(seconds) / 60) % 60;
int seconds_left = int(seconds) % 60;
cout << "Training until now has taken " << days << " days " << hours << " hours " << minutes << " minutes " << seconds_left <<" seconds." << endl;

This worked perfectly under Windows 7 and had been working under Ubuntu 12.04 also, but lately I am getting reports of training times which take up to multiple hours but when I take a stopwatch to measure it myself, only 40 minutes have past or so. Keeping this bug report mainly to investigate the cause of this!