Depending on the operating system the way the actual fix is implemented can vary.
The first thing to establish is whether the clock is running at the correct speed, and it is only the time it is showing consistently out by the same amount. If it shows a certain time, turn it off completely for 10 minutes and remove the power (and battery is it is a laptop with a removable battery). Then power it up again and check the time. If it has advanced about 10 minutes, then the basic clock circuits appear to running properly. If not, then there is probably a small button cell battery inside that needs replacing. This cell keeps the internal clock chip working when the computer is turned off. This could need professional help to replace the cell.
Assuming the clock is keeping time, but showing the wrong time, then the next step is to check what time zone the computer is set to. In Windows, go through the settings until you find the time zone setting and adjust it as necessary. Also check if there is a separate Daylight Saving Time option and if there is set this appropriately.
Next, check that the date is correct. Some systems will not set the time automatically if the date is wrong.
Next, assuming you have an Internet connection, check to see if the computer is set to get the time from the Internet. If it is, turn this off and then turn it back on again, which should get a new time setting from the Internet. If you have no Internet connection, or it is failing to get the time automatically, then you can try turning off the automatic setting and then set it by manually. The clock may gradually drift when set to manually configured time, so you might want to adjust it occasionally if it gets too far out.
If you are still having issues, then consult the vendor or the manufacturer for further assistance.
I hope this helps.