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How To Maintain Accurate Time On Your PC

Published by Sami

PC How To Maintain Accurate Time On Your PC

PC's have internal real time clocks designed to maintain system time. The internal clocks rely on relatively low-cost crystal oscillators, which are notoriously inaccurate. In many cases PC system time can drift by several minutes each day. This article describes various methods of maintaining a highly accurate time on your PC. It describes how to utilise Internet time references, radio and GPS clocks and dedicated NTP server systems.

Internet Time References

The Internet utilises the Network Time Protocol to distribute accurate time information to network time clients. NTP has been an important part of the Internet for over 25 years. The protocol was born through the need to provide synchronisation of time critical processes across the Internet.

Most modern operating systems, including Windows XP, 2003 and LINUX have the ability to synchronise time with a NTP Server. There are a host of Internet based NTP Servers with public access that can be used to synchronise your PC. Below is a list of popular Internet based public access NTP Server references: - US based time reference. - German time reference. - UK time reference. - French time reference. - Canadian time reference.

Windows XP has pre-installed SNTP client software that can synchronise time with a NTP server. This is achieved by simply entering the domain name of an Internet NTP Server in the time properties tab. The host computer will then periodically contact the NTP Server and synchronise the system time to the specified reference.

LINUX and UNIX systems have the NTP software distribution available from the NTP website, The NTP application runs as a daemon, constantly monitoring specified NTP servers. The application reads a list of NTP servers from a configuration file, 'ntp.conf', and periodically synchronises time. A list of NTP server references is specified with the 'server' configuration command thus:

server # NIST, Gaithersburg, Maryland NTP server server # NIST, Boulder, Colorado NTP server

Once configured, the NTP daemon can be started, stopped and restarted using the commands: 'ntpd start'; 'ntpd stop' and 'ntpd restart'.

Radio and GPS Clock Timing References

There are many commercially available radio and GPS clock timing references for PC's. Radio and GPS clocks obtain accurate time from national radio timing references or from the GPS system. The devices have serial or USB interfaces and provide an accurate timing reference to PC's. Driver software periodically synchronises the system time of the host computer to the received reference time. Often reference clock drivers are available that interface to the NTP application software to provide your own dedicated NTP server.

Radio time receivers often have the advantage of having the ability to obtain a good signal, indoors, close to the host computer. However, the signal can only be received locally to the transmitter. There are a number of radio time broadcasts available: MSF transmitted from Rugby, UK; DCF-77 transmitted from Frankfurt, Germany; WWVB transmitted from Colorado, USA; CHU, Canada and TDF, France. GPS has the advantage of providing a global time and frequency solution; however, an externally located antenna is required which can be impractical.

Dedicated NTP Servers

NTP servers are dedicated time servers that obtain time from an external source, such as radio or GPS, and provide a network with an accurate timing reference. NTP servers are generally rack-mountable devices with an external antenna and an Ethernet connection. The devices obtain time from a radio or GPS timing reference and maintain an accurate internal time. The accurate time is then distributed to network time clients over an IP network. Dedicated NTP servers often minimize the set-up and configuration effort required to get a NTP server installation up and running.

About the Author

Dave Evans develops NTP Server synchronisation systems to ensure accurate time on PC's and computer networks. Dave has been involved in the development of dedicated NTP server systems, NTP synchronised digital wall clock systems and atomic clock time synchronisation products. Find out more about SNTP and NTP Server Systems at:
Radio NTP Server MSF-60 DCF-77 time synchronisation

By codezmith on 02-21-2007, 08:25 PM

elo ! just joined grabed sum files ,coffy n scaned over ur article
it reminded me of this :atomic-clock/
and my lack of trust for M$ ,xp(espeshly)
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\Curr entVersion\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\Servic es\W32Time\TimeProviders\NtpClient]
Value Name: SpecialPollInterval
Data Type: REG_DWORD (DWORD Value)
Value Data: Seconds in Decimal
Quote: offers:

* A more complete list of countries
* Map and Globe graphics to help you place each location geographically
* More accuracy with Daylight Saving adjustments made at the same moment that locations actually change to and from DST
* More link options, including a flash-based analog clocks or a search boxes you can embed on your web pages

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By shubham on 02-22-2007, 07:27 AM

its great prevelage for me that i m having a excelent support from u & getting a different software

thank u
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