PC's are notoriously poor at keeping time. I am sure the you have probably noticed the time on your PC drifts away from the correct time by a number of seconds or even minutes each day. This is because real-time clock chips, used in modern PC's, use similar components to every-day clocks and watches and are just as prone to drift away from the correct time. However, there are things that you can do to maintain accurate time on your PC. This article discusses ways in which you can maintain continuously accurate system time on your computer system. It looks at how Internet time references and NTP servers can be utilised for computer time synchronisation.

There are a large number of Internet based time references that use the Network Time Protocol (NTP) to synchronise time clients. Dr David Mills of the University of Delaware introduced NTP over 25 years ago. The protocol was developed to provide accurate synchronisation of time between time servers and clients. Internet based NTP servers synchronise their time to accurate external reference clocks, such as GPS, national radio time standards or precise atomic clocks. Accurate time is then passed from the NTP server to network clients for synchronisation.

Many modern operating systems have integrated functionality to synchronise with NTP server systems. Linux, Unix, Microsoft Windows XP/2000/2003/Vista and Novell all have routines for NTP time synchronisation. For the most part, the only configuration that is required is to enter the IP address or domain name of an Internet or Intranet based NTP server.

Windows XP/2000/2003/Vista machines can accept the IP address/domain name of a NTP server in the time properties/internet time tab. Periodically, the NTP server will be contacted to obtain time and perform synchronisation.

The Linux and Unix operating systems have a NTP daemon available from the NTP web site at 'ntp.org'. The daemon can act as a server or client and can easily be configured to synchronise with an Internet based NTP server. The 'ntp.conf' configuration file contains a list of servers that can be contacted. Simply enter the IP address or domain name of a NTP server in the list.

To maintain accurate time on a computer system using NTP is very straightforward. However, there are many other more advanced features of the NTP protocol. There are security and authentication facilities that allow a server to limit client access and a client to authenticate a server. Additionally, there are numerous reference clock drivers available to synchronise NTP with a precise external reference - providing a full-blown NTP server installation.

To summarise, PC clocks are very inaccurate and can drift by several minutes each day. For applications where time synchronisation of processes is critical or even if you just want the correct time on your computer, standard time keeping is inadequate. The solution is to use the NTP protocol and get your computers synchronised to some of the most accurate clocks in the world.