An normal ECG (electrocardiogram) consist of P, Q, R, S and T waves.
P wave indicates initiation artrial depolarisation (contraction) and the time between P to Q is the artrial depolarisation time which is 0.1 sec.
The QRS is related with ventricle depolarisation (contraction). The wave QR indicates initiation of ventricular depolarisation and the interval RST indicates ventricular depolarisation time which is 0.3 sec.
The wave T indicates initiation of complete/joint diastole of both the auricle and ventricle and the time of joint diastole is 0.4 sec.
That's way a beat completes in 0.8 sec (i.e. auricular + ventricular contraction = 0.4 sec and joint diastole of both is 0.4 sec thus total = 0.8 sec).