Synchronising the System Clock with the Internet

System Clocks are Not That Accurate

Computers are supposed to be highly accurate, so you might think that system clocks would keep very good time, but they rarely do. This is because there’s no good reason why one computer needs to run at exactly the same speed as another. If you look at two computers that both nominally have their central processor units running at 2 GHz, the chance of them both running at exactly that speed is exceedingly small. They probably both run at slightly over 2 GHz, otherwise they should never have been advertised as running at that speed, but they won’t be precisely the same.

Clocks Need Synchronising from Time to Time

Even top-quality watches drift slightly and need to be corrected from time to time, which is why the standard ‘synchronise watches’ scene has been incorporated into so many war films. The primary function of a computer is not to be a very large and expensive watch, but to perform computations as quickly as possible, so slowing down a slightly fast computer to match other slower machines would be pointless.

Clock Synchronisation in Windows is Not Great

Having said all this, there’s a way to make sure that your computer’s system clock remains reasonably accurate. From time to time, your computer can correct its system clock by synchronising with one of the highly accurate atomic clocks connected to the Internet. However, Windows sometimes has trouble doing this. If you notice that the system clock is out of step with reality, you can click a button asking for the clock to be synchronised with an Internet time server immediately. However, this process often fails with an unexplained error. The best solution is to install a third-party program called ‘NetTime’, which is available from and keeps your system clock accurate without any human intervention.