Date of client changing constantly

Once I faced the problem of changing date of my many client computer which are under one domain, keep changing the same date . I got fed up finding the problem, i install the new updates for antivirus and install new adwares and malwares removal and scanner and removed all the temporary files but could not find that problem. At last when i see that the date it taking is same on another computer so i tried to see the date of the server which was reset to its default date so they were taking that date . when ever i used to change the time it was just for few minutes and changed to default due to which i could not surf the internet

 Generally In one computer once the pc is switch on it should not be due to battery problem that time keeps changing .