date and time changes to 12/5/2013 at random times
After I updated to El Capitan (it would seem) on my iMac. My system date and time randomly change back to 12/5/2013 and the incorrect time. I don't see anything in particular triggering it. Just all of a sudden my browser wont open a page... etc. I open the system preferences, click on "date and Time", click the lock to open it, enter my password and it immediately changes back to the correct date and time the second it unlocks. I don't have to reset it myself. I've tried leaving the lock open, unchecking the "do it automatically" box & leaving it auto. Can anyone offer any suggestions as to why and how to fix this, please? Thank you
iMac (27-inch, Late 2012), OS X El Capitan (10.11.3)