Computers are generally very poor timekeepers. They rely on low-cost timing components that are widely used in general-purpose clocks and watches and are just as prone to drift. The real-time clocks and cheap crystal oscillators integrated on to PC boards can cause system time to drift by several minutes each day. However, there are software solutions on hand to correct time drift and maintain accurate system time on your computer.

This article describes techniques that can be used to eliminate system clock drift and keep precise time on your computer and across your network. It describes how Internet based time servers and the NTP time protocol can be used to keep accurate synchronised time on your computer. There are a large number of Internet based time references that use the Network Time Protocol (NTP) to synchronise time clients. NTP was developed over twenty-five years ago at the University of Delaware by Dr D. Mills, it remains one of the oldest protocols in constant use.

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. Precise time is then disseminated around the network for the purpose of 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. Generally, client-side configuration consists of providing the client with the domain name of the 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. Without help, standard time keeping devices are just not up to the task of providing system-wide time synchronisation.

The solution is to use the NTP protocol and get your computers synchronised to some of the most accurate clocks in the world.

The author of this article, D. Evans, is a well-respected technical author in the field of NTP server systems and computer network time synchronisation. D. Evans is the author of many articles and white papers detailing the instillation and configuration of computer network timing systems. A number of articles also discuss precision timing references for NTP servers such as TCXO, OCXO and rubidium oscillators. Please go to our web site for more information about NTP server systems.