BOOT CAMP 308 (12/01/04)




As so often happens this week’s topic was inspired by reader emails, two of them to be precise, though it was the lack of precision that sparked the whole thing off.


It wasn’t so much the content of the emails that caught my eye but the time and date they were sent. The first was apparently written four years ago, on January 1st 1999, which stretches credulity somewhat, even with the Internet creaking under a deluge of Spam. The second email was even more remarkable as it bore the date June 2006. The message referred to a previous week’s Boot Camp and I concluded that it probably wasn’t from the future, though I emailed the sender for a list of forthcoming Lotto numbers, just in case…


The ‘sent’ time and date stamp on an email is determined by the PC on which it originated and it’s interesting to see how many computer clocks are set wrongly. A random survey of the sent times of emails in our inbox suggests that at least half of Connected reader’s PCs may be more than five minutes adrift. You can check the accuracy of your PC clock (to the nearest second) by going to:


Normally it doesn’t matter too much if the clock on home PCs run a little fast or slow, in fact it is inevitable due to the way most computers keep track of time. The worst that usually happens is emails and saved files are incorrectly time-stamped. However, accurate timekeeping can be vitally important on PCs used to keep business records or conduct financial transactions, but in any case it is worth knowing a bit about how PCs keep track of time, and what you can do to improve accuracy.


PCs have two clocks; the first is the hardware or ‘real-time clock’ (RTC), a small battery powered module on the motherboard that maintains timekeeping when the PC is switched off, disconnected from the mains or a source of power. It is controlled by a quartz crystal and accuracy can easily wander by 10 to 15 seconds a day due to variations in temperature. The battery powering the clock generally lasts for between 3 and 5 years and towards the end of its life the clock will slow down or become erratic. Look out for warning messages at boot up, including the really helpful ‘CMOS checksum invalid’, and ‘Invalid configuration run Setup’. Replacing the clock battery is not usually too difficult, and they normally only cost a pound or two but seek expert help if you don’t fancy the idea of opening up your PC.


The second PC timekeeper is the ‘software’ clock, which is built into Windows. At boot up Windows receives data from the RTC to set the clock and then uses system timing signals to keep the display clock ticking. The accuracy of these timing signals varies, depending on what else the PC is doing. Clocks on older PCs using early versions of Windows could loose several minutes a day just by running a couple of applications. Accuracy improved dramatically from Windows 98 onwards and the clock in Windows XP is largely unaffected by the PC’s workload, nevertheless, the time on all standalone PCs can and does drift if the only source of reference is the RTC.


There are several ways of ensuring that your PC clock is correct. You can set it manually from an external time signal, such as the ‘pips’ on the radio, the Speaking Clock or Teletext but this can become tedious if you have to do it every day. There used to be a range of gadgets, like super-accurate temperature–compensated clocks and ‘MSF’ radio time receiver modules but these days the best way to ensure accuracy is to log on to a ‘Network Time Protocol’ (NTP) server on the Internet. These are web sites that provide highly accurate time and date information derived from atomic clocks. Delays and errors introduced by the Internet, including the distance between the PC and time server, can be compensated for and it’s possible to ensure that your clock is never out by more than a second, as well as checking and correcting for any errors in the PC’s date settings.


Windows XP has an Internet time facility built in. When online double-click the clock display, select the Internet Time tab, click the Update button and Windows checks and synchronises the clock with the two default NTP servers (for a list of alternative time servers go to: After than XP automatically checks the time once a week. For a list of Internet time sync utilities for earlier versions of Windows see Tip of the Week.


Next week – Transferring Outlook Express





By analysing the vibrations of certain atoms (Cesium is the favourite) it is possible to measure time to an accuracy of a few billionths of a second per day



Complimentary metal oxide semiconductor - family of low power microchips used to store and process digital data



The call sign of a radio signal containing time and date codes, generated by an atomic clock, broadcast by the UK National Physical Laboratory near Rugby on a frequency of 60kHz




There are a number of utilities for Windows 9x (95/98/ME/SE), to check and correct your PC clock and date settings every time you log on to the Internet or at scheduled intervals. The freeware offerings are often just as good and in some cases even better than the commercial programs so have a look at: Time Synchronizer (, DS Clock ( and SymmTime (

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