Atomic Clock Sync is a freeware utility that synchronizes the PC clock with the US National Institute of Standards and Technology (NIST) servers and thus provides the best possible time accuracy.

The interface is clean and pretty straightforward, with all features organized in nifty tabs listed at the top of the main window.

You can thus view the “Current Settings”, choose the “Synchronization Interval” and “Repair Service” in case there's something wrong with the Windows Time Service.

The first screen comes with a pretty intuitive name and provides information such as local time, daylight time zone name, date and bias. The second tab is the one that's more important, letting you choose the synchronization interval to automatically adjust the time using the NIST servers.

By default, the application performs the synchronization once a week, but that can be easily changed to as often as you like.

In case the Windows Time Service doesn't work as it is supposed to, Atomic Clock Sync has dedicated tools to register/unregister and stop/start the service.

Everything works like a charm on all Windows versions and it takes just a second or two until the program adjusts the time. Windows 7 users may need to run the tool with administrator privileges and set an exception in the Windows firewall in order to allow it connect to the NIST servers.

Overall, Atomic Clock Sync does a great job and remains light on computer resources all the time. It can automatically synchronize the time and, what's more, it is offered with a freeware license.