MacOS – How to keep the system clock in sync under Mavericks

I have a mid 2011 27" iMac running Mavericks (10.9.1). I updated from Mountain Lion this Fall when Mavericks was released. I never had any problem before with my system clock.

Since installing Mavericks my clock consistently gains about 20 seconds per day. I have my Time Zone correctly set and "Set Date and Time Automatically" is checked in my Date & Time system preferences. It is set to use "Apple/Americas/U.S. (time.apple.com)"

When I open the Date & Time System Preferences pane my clock gets adjusted immediately to the correct time, but without opening the pane, it gets off track pretty quickly.

I have rebooted, checked and unchecked the box to set the date and time automatically and neither seems to have helped.

Any solutions or ideas?

UPDATE:

I have made what feels like progress. Question: How can I tell if my mac is keeping the clock updated properly? and its accepted answer by grgarside provided a lot of helpful troubleshooting help. My drift is a whopping 499.988 (gains 43.19 seconds per day)!

Most importantly, pacemaker is running every 5 – 15 seconds, as evidenced by my stem log, however, every time it runs it gets an error:

Feb  1 11:53:29 jsw.local pacemaker[19928]: adjtime: Operation not permitted
Feb  1 11:53:39 jsw.local pacemaker[19928]: adjtime: Operation not permitted
Feb  1 11:53:51 jsw.local pacemaker[19928]: adjtime: Operation not permitted
Feb  1 11:53:59 jsw.local pacemaker[19928]: adjtime: Operation not permitted
Feb  1 11:54:09 jsw.local pacemaker[19928]: adjtime: Operation not permitted
Feb  1 11:54:19 jsw.local pacemaker[19928]: adjtime: Operation not permitted

It seems I have a permission problem, but I cannot figure it out. I have unloaded and reloaded the pacemaker plsit via launchctl

sudo launchctl unload /System/Library/LaunchDaemons/com.apple.pacemaker.plist
sudo launchctl load /System/Library/LaunchDaemons/com.apple.pacemaker.plist

here is a text export of my com.apple.pacemaker.plist

{
    Label = "com.apple.pacemaker";
    ProgramArguments = (
        "/usr/libexec/pacemaker",
        "-b",
        "-e",
        "0.0001",
        "-a",
        10,
    );
    KeepAlive = {
        PathState = {
            "/private/var/db/ntp.drift" = YES;
        };
    };
}

my /private/var/db/ntp.drift file is owned by root:wheel and its permissions are 644, /System/Library/LaunchDaemons/com.apple.pacemaker.plist has exactly the same ownership and permissions.

I hope this update provides enough additional information so that someone can get me past this issue.