Computers utilise real time clock chips to maintain system time. These timing devices rely on relatively cheap components, which are generally poor at maintaining accurate time. A computer systems time can typically drift by minutes each day. This article discusses a number of methods of keeping a computers system time accurate. From utilising Internet based NTP servers to using GPS and radio time references, it attempts to shed light on how to keep your computer synchronised.

One of the most cost-effective and accurate ways to obtain precise time is to use an Internet based time server. These servers use the NTP protocol to distribute accurate time. NTP is an acronym for the Network Time Protocol, which has been an important part of the Internet for over 25 years. It was born through the need to provide synchronisation of time critical processes across the Internet.

Many operating systems, including Microsoft Windows servers and workstations and LINUX/UNIX machines have the ability to synchronise time with a NTP Server without any additional software. Often all they need is to be configured correctly. There are a host of subscription-free public time servers across the internet, many of them provided by Government agencies and departments. Providing your computer has access to the Internet, the chances are that you can sync to one of these servers.

Microsoft Windows XP has a pre-installed SNTP client service called 'Windows Time'. SNTP is Simple Network Time Protocol, which is effectively a simplified subset of NTP. The Windows XP time service uses SNTP to sync time with NTP time servers. This is achieved by simply entering the domain name or IP address of an Internet based server in the time properties tab. The host computer will then periodically contact the server and synchronise its system time to the specified reference.

LINUX and UNIX systems also utilise the NTP protocol. In fact, the protocol was originally developed for the Linux operating system. If not pre-installed, the NTP software distribution is freely available from the NTP website under the GNU public licence. The application runs as a daemon, constantly monitoring and synchronising to a specified list of NTP time references.

If an Internet connection is unavailable, you may need to consider a hardware time reference. These devices have computer interfaces and use external reference clocks, such as GPS and radio to provide precise time.

The GPS system is primarily intended for navigation purposes; however, few people realise that it can also act as an extremely precise time reference. GPS devices with serial or USB interfaces can provide accurate time and positioning information to computers. Software drivers periodically obtain time from the GPS device to synchronise the system time of the host computer. Often, reference clock drivers are available that interface to the NTP distribution to provide your own dedicated time server.

Radio time receivers utilise time and frequency transmissions generated by national physics laboratories. They have the ability to receive a radio signal indoors, thus potentially reducing installation costs. There are a number of world-wide 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. These signals can often be received up to a few thousand kilometres away from the radio transmitter.

Internet based dedicated Stratum 1 NTP servers utilise GPS and radio hardware clocks for synchronisation. Indeed, by using the NTP protocol and a hardware reference clock, you can easily maintain your own network time server.

Why not find out more about computer and network time synchronisation and NTP Server systems.