FerenSoft.com - Tip of the Month - Computer Clock Always Off

FerenSoft Computer Tip
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“Computer Clock is Always Off”

Timely Batteries

Did you know that most computers have two internal clocks that track the time and date? The one you are most apt to know about keeps the computer's time and date you see when the machine is on. This main clock draws its power from the running computer, and usually reports the correct time and date. It can only run when the computer is actually on.

The second clock keeps track of time when the computer is off, and draws its power from a small battery. This battery will eventually weaken and cause the secondary clock to lose both “ticks” and time. At first it is trivial, but it can begin to drift as much as several hours overnight!

When you turn the computer on in the morning, the startup process asks the second, battery-powered clock for the current time and date, assumes the answer is correct, sets the system's main time clock (the one we see) to match, and then goes about its other startup business.

However, if the battery-powered clock that keeps time drifts, due to a weak battery, the startup process won't know any better, and will assume the wrong time. When this happens, the result is almost always a “late” clock, meaning the computer's main clock reports a time that in our reality has already come and gone by. After a long weekend the date may be wrong as well.

When the main computer clock is wrong it can always be set from some clock related control in the Windows, Mac or Linux operating systems, from the Command Prompt, or even from the computer's hardware setup screen. All of these techniques will correct the time and date reported by the clock, at least until the computer is turned off. Once the machine is turned off, the battery powered clock will resume its lazy time-keeping chores.

No battery lasts forever, but eventually weakens. They can last from 1 to 5 or more years, depending on which of the several types of battery your particular hardware uses. When you begin to notice your computer's clock drifting significantly, this is not a problem with any of your software, nor with your computer, per se, but with the secondary clock's battery, which you need to replace.

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