If your PC is more than around 5 years old, here’s a problem you may well run into. There are various ways in which you might discover it’s happened, and a friend of mine found out in quite an unusual way. At many of the websites he visited, he saw a message like this:
“There is a problem with this website's security certificate. The security certificate presented by this website has expired or is not yet valid. Security certificate problems may indicate an attempt to fool you or intercept any data you send to the server.”
Effectively, whenever he arrived at a ‘secure’ web page (one whose address starts with ‘https://’), he was being told that the page wasn’t secure at all, and therefore wasn’t to be trusted. The security certificate issued to the website to prove its authenticity had the wrong dates on it: either it had expired, or it didn’t become valid until some future date.
If this happens on just one website, there’s obviously a problem with that site’s security and it’s not to be trusted. However, if every secure website has the same problem, there’s something more unusual going on. I asked him to check the date and time on his PC by holding the mouse over the clock on the taskbar and, sure enough, it was shown as being a little after midnight on 1st January 2003!
This little error prevented him from accessing his online banking page.
This wrong date on his PC is the culprit. When his web browser checked the issue dates of the security certificates at websites he visited, it found that those certificates were not due to become valid until some date well into the future – in other words, well after January 2003 – so it understandably felt there was a security problem with the sites.
This is an unusual and roundabout way of discovering your PC’s date is wrong, as I mentioned earlier. More common ways are to find that every email message you send was seemingly written years ago, or to notice that the clock doesn’t tell the right time (or show the correct date).
The reason this can happen is due to something you may have idly wondered about: how your PC ever knows the correct date and time when it spends so much of its time switched off. The answer is that these details, among others, are stored in a computer chip named the ‘CMOS’ (pronounced see-moss) and a tiny battery powers this chip. When that CMOS battery is on its last legs, one of the symptoms is that it loses track of the date and time. You’ll either start seeing very erratic dates and times or you’ll find the time set to midnight on 1st January of some long-past year.
The CMOS battery is a little disc-shaped battery of the type used in watches, and it generally has a lifetime of 5–10 years. If you discover that your own PC’s CMOS battery needs replacing, it’s a cheap part to buy, and a quick and easy job for someone who knows their way around the innards of a PC.
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