The duration of atrial systole is:
When the heart beats at a normal rate of 72/minute, duration of each cardiac cycle is about 0.8 second. 
ATRIAL EVENTS 
Atrial events are divided into two divisions: 

Atrial systole = 0.11 (0.1) sec.
Atrial diastole = 0.69 (0.7) sec. 

VENTRICULAR EVENTS 
Ventricular events are divided into two divisions: 

Ventricular systole = 0.27 (0.3) sec 
Ventricular diastole = 0.53 (0.5) sec. 

In clinical practice, the term 'systole' refers to ventricular systole and 'diastole' refers to ventricular diastole. Ventricular systole is divided into two subdivisions and ventricular diastole is divided into five subdivisions.
0.80 second
0.57 second
0.11 second
0.44 second