System time not updating while screen is locked
Wiping cache with stock recovery seems to have solved it for me.

Power off phone (be sure to turn off fast reboot in settings first). Boot into recovery by holding volume-down key and then holding power key until boot menu appears. Volume down to RECOVERY and tap power to select. HTC logo appears followed by a blank, dim screen. Wait about 30 seconds for red triangle icon to appear.
Now, hold down volume-up and tap power button. Recovery menu appears. Volume-down to &quot;Wipe cache partition&quot; at bottom of list and tap power key. Cache gets cleared. Then select &quot;reboot system now&quot; by tapping power key again. Done!