Clocks are essential for computers. Everything from sending and email to turning a PC on will involve a timestamp. Computers are reliant on knowing when processes happen and when they need to happen.

However, the internal clock chips on a computer, known as Real Time Chips (RTC) are mass manufactured and are optimized for economy and not accurate time keeping. As a result the clocks on computers are prone to drift.

This doesn’t cause too many problems for the home user; emails may arrive before they are sent but for day-to-day tasks perfect synchronization is not too important.

However, an inaccurate clock can leave a system open to abuse and for computers acting as servers a lack or synchronization can cause untold havoc particularly if all machines on a network are telling different times.

However accurate time on a PC is relatively straightforward to achieve as the world’s leading protocol for ensuring time synchronization, NTP (Network Time Protocol) is already installed in Windows and UNIX.

Note: some operating systems contain a simplified version of NTP (SNTP) but is is quite adequate for most time synchronisation applications, if more precise time is required then NTP (currently on version 4) is available free via ntp.org.

NTP has been developed over the last 25 years and is without doubt the best timing synchronisation protocol available (there are others on the market but 99.9 percent of time servers use NTP).

NTP is used by a computer network to synchronise to an absolute source, a timing reference from an atomic clock that relays the world time scale UTC (Coordinated Universal Time) either via the Internet or from a national time standard radio broadcast or even the GPS network.

For most modern operating systems to synchronise to an absolute UTC source over the Internet is incredibly easy with just the domain address needed to be entered. In Windows this is done by clicking the Internet time tab on the time properties box (double click the clock) for Linux and Unix the domain address can be entered in the ntp.conf file.

It must be noted however, that Microsoft and others suggest an external hardware source is used as Internet timing references can’t be authenticated, leaving a system open to abuse or a malicious attack.

There are a multitude of external time servers available the majority of which use NTP to connect to either a radio transmission (only possible if a signal from a national transmitter is obtainable) or the GPs network (though a GPS antenna connected to the Internet).

With a GPS or radio referenced NTP time server accuracy of a few milliseconds can be achieved relatively easily.