Free! - Atomic Clock Sync utility

Our freeware Atomic Clock Sync utility can help you keep your local computer up-to-date with the exact current time.

This program will reference an atomic clock server to get the current time with the greatest accuracy available and update your PC's information. It can even be set to automatically check the time once a day to keep your PC's time accurate forever. Best of all, you can download and use this utility at no cost to you! It is simply our free gift, no questions asked, just to encourage you to return to World Time Server whenever you need current times elsewhere around the world!

download Atomic Clock Sync 2.7.0.3 Download.com

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(this free utility requires Windows XP, 2000, Me, 98, 95 or NT 4)

Atomic Clock Sync is provided free of charge by
World Time Server

About this utility

This program will connect to one of the time servers operated by the National Institute of Standards and Technology (NIST) in the United States, and will compare the time of your computer with the time on the servers operated by the NIST. This program will then display the difference between your system and the servers and if greater than 15 seconds, it will offer you the option of adjusting your PC by the displayed amount.

The overall uncertainty in this comparison should be no worse than +/- 5 seconds under all circumstances and will be substantially less than this value in most cases.

This utility is provided free of charge, so please feel free to share it, redistribute it, and use it any way you wish, provided you do not alter the program in any way.

Version 2.7 offers new options to have Atomic Clock Sync start automatically when Windows boots up and to have it start minimized to the system tray.

Some users were having trouble connecting to a functioning time server and were getting an error regarding "not an integer", which has been corrected in the current version.

Understanding the Display

The main screen displays Current UTC, which is the current Universal Time Coordinated that all locations base their time on. This is also sometimes referred to as Greenwich Mean Time or Zulu Time.

Currently In shows whether your local pc's time zone setting claims you are currently observing Daylight Time or Standard Time.

Standard Time Zone Name with Date and Bias and Daylight Time Zone Name, Date and Bias show your local computer's current time zone rules. These rules come from Windows and are set when you select a particular Time Zone in your Date/Time settings.

Unadjusted UTC Bias shows how many hours your local time zone is offset from the current time in UTC.

Date & Time of Last Successful Ping allows you to see how recently ACS checked with a server to compare times with your local clock.

Please note that your actual current time is not shown in ACS, only your System Settings. Your current time should always be available to you in the lower right corner of Windows in the System Tray.

Atomic Clock Sync Settings in Windows XP

While WorldTimeServer.com can help you look up accurate times around the world, we see lots of interest from our users in keeping your local computer clock accurate, too. Atomic Clock Synchronization is the best way to make this happen.

Most of the visitors to this site are using Windows XP, which has an atomic clock sync feature built in and included as part of your operating system. If you have Windows XP and wish to check your synchronization settings, look for the clock at the bottom right and double click on the time to bring up your time settings. You can adjust your local time and date by hand on the first tab, you can adjust your time zone location on the second, and on the third, labeled Internet Time, you can view your current atomic clock sync settings.

A few things to notice about this screen:

The checkbox must be checked for XP to compare your local pc clock with an atomic clock server on a scheduled basis.
The server list lets you pick from a short list of time servers (usually only neccessary when the current server you are using is giving you an error).
You will see the results of the last time check, which in this screen shot, shows a successful sync as well as the time it took place.
Near the bottom is a "Next synchronication:" value which will let you know how long it will be until XP checks your local time accuracy again.

Some common questions from advanced users might be "Can I add more time servers?" and "Can I synchronize more often?" The answer to both is a qualified yes ... if you have administrative rights on your PC and are comfortable editing the registry.

Disclaimer: Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.

To add more time servers, find the registry key for DateTime Servers provided in full below and create a new string value. Name it the next number in sequence (usually '3') and set the data of the new value to equal the hostname or IP address of the time server.

You can also change the default server by setting the value of "(Default)" to the entry number of the required server.

System Key: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\DateTime\Servers]
Value Name: (Default)
Data Type: REG_SZ (String Value)
Value Data: Server Hostname or IP Address

To synchronize more often, find the W32Time registry key given below modify the existing value called "SpecialPollInterval". If you don't see SpecialPollInterval listed in this section, you can create it as a new DWORD value. The value of this should be set to the number of Seconds between sync attempts. If you wanted to check once per day, the value would be 86400.

System Key: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient]
Value Name: SpecialPollInterval
Data Type: REG_DWORD (DWORD Value)
Value Data: Seconds in Decimal