My clock is slow over long period of time - Macbook Pro 2011 13" When i leave my macbook alone for a day (doesn't matter if it's asleep or off), and access it after, my clock is always slow about an hour.

I know this isn't an OSX issue, cause i use bootcamp too and the same thing happens there.

It also doesn't matter if i'm on battery or if i'm plugging in.

I'm certain it's not a time zone issue either... it can be slow 35 minutes, or slow 135 minutes, depending on how long i leave it alone.  Its like the macbook is living in another time dimension.

Some piece of hardware on the macbook that is responsible for keeping the time is messed up... but i don't know what that piece of hardware is and if i can replace it.

Can someone tell me?
The clock time is keep by a battery or capacitor on some models. It is a small battery on the motherboard and used when the computer is off.

When the computer is on and online it will automatically update the clock time.

Normally that battery last 3-5 years. 

Try setting the time manually, by getting the actual update for apple time server.


  sudo ntpdate -u time.apple.com


then you will see something like


  8 Jun 14:30:11 ntpdate[28267]: adjust time server 17.151.16.14 offset
  0.000336 sec


You generally don’t need to do this if you use the “Set date and time automatically” feature within the Date &amp; Time settings.



If that did not work, reset your SMC and PRAM (System management Controller)

I can not believe it is your battery but everything is possible :(. Assuming you do not have 2 left hands, you could do that your self.