I have a 2012 13" MBP that I leave on almost aways. I notice the longer its left on, the more the time gets out of sync. It's only off by a few minutes but is annoying. Opening the Date & Time Preferences easy fixes the issue and it syncs back up without any help from me but why is this happening? Any way to fix it? I have the checkmark in Set date and time automatically to "Apple Americas/U.S. (time.apple.com).". Not really sure why the . is after the .com but it is for all the options in the drop down location. My Mac Mini which I leave on 24/7/365 as a server has zero issues keeping time.