Introduction
On windows based PC's, laptops and tablets the time is normally obtained from a quartz crystal based clock that is maintained by a lithium ion battery on the motherboard of your computer.
In general you can expect time drift of 2 or more seconds per day (compared to about 1 second every 3 days from a typical hardware token), but can be greatly improved if the PC is automatically synchronised with an external source (either an internet time server or the clock on the local domain controller).
Correcting the time on a windows computer
There are many possible solutions to identifying and correcting the clock on your local computer, but one of the simplest is by using the service provided by time.is
After opening a browser window to the TIME.IS web page you will be presented with a clear indication of any drift between you computers clock and the remote time server;
As can be seen in the above example the test computer was less that 1 second out when compared with the remote time server.
If significant time drift is detected, you would be advised to configure your computer to automatically update the clock using and external time server.
You can correct the system clock on the PC using either the following methods;
Launch the control panel by (press
, type "cmd" then click 
)
The command prompt window will now open;
Issue the command "Time", then at the prompt "Enter the new time:" supply the time currently show on the TIME.IS web page
Launch the control panel by (press
, type "control panel" then click )
From the control panel click on the
icon
To update the clock manually, select the "Date and Time" tab to display, then click on
;
Alternatively, you can click on the
tab, then use the 
button to synchronise with an external time server using the 
button (example below);
Launch the systems settings window (by pressing
), then select "Time & language");
The heading will now change to "Time & language", click on the section "Date & time";
Ensure the "Set the time automatically" option is turned on;
Once this option has been enabled you will be able to synchronise the PC's clock with the external time server by clicking on the "Sync now" button;
After updating the system clock you can confirm the clock is now synchronised correctly by revisiting the TIME.IS web page and your computer clock should now be accurate to less than 1 second.