How To Change the Date and Time in Windows XP
1/ Start Windows XP normally. Make sure you are logged in as an administrator or as another user with privileges for changing settings.
2/ Click on the time that is displayed in the task bar. This will bring up the Date and Time Properties box. You can also right-click on the time by clicking on the "Adjust Date and Time" menu option.
3/ Highlight a portion of the time on the digital clock, beneath the graphic representation of the time (it looks like a traditional round-faced clock), to highlight it. Make sure you have highlighted the correct portion (hours for hours, minutes for minutes).
4/ Enter the time you wish to change and click "Apply."
5/ Click one of the drop-down menus in the "Date" section of the window. This will allow you to change the month and the year, either by typing them in or selecting them from the menu.
6/ Click on a particular day of the week to reset the calendar to that day.
7/ Remember to click "Apply" whenever you change a property or multiple properties. Your changes will not be confirmed until you do.
8/ Enable the daylight-savings time function in the "Time Zone" tab. This will automatically change the clock to conform with daylight-savings time.
How To Change the Date and Time in Windows Vista
1/ Click on the Control panel from the Start menu.
2/ Go to "Clock, Language and Region."
3/ Click "Date and Time."
4/ Click the "Date and Time" tab and then "Change Date and Time." Enter your password if prompted to do so.
5/ Double-click the hour. Click the up or down arrows to set the correct hour, or type it manually.
6/ Double-click the minutes. Use the up or down arrows to set the correct number of minutes after the hour, or type it manually.
7/ Select the correct month from the dropdown menu on the calendar to the left of the clock.
8/ Click the correct date on the calendar.
9/ Set the correct year by using the up or down arrows next to the box with a year in it.
10/ Click "OK" when you have finished setting the date and time.
11/ Select "Change Time Zone" to change the time zone on your computer.
12/ Choose your preferred time zone from the list on the "Time Zone Settings" dialogue box.
13/ Select the "Automatically adjust clock for Daylight Saving Time" box to have your computer's clock automatically updated for Daylight Savings.
14/ Hover your mouse over the clock on the right side of the desktop to change the time from the sidebar.
15/ Expect two buttons to appear: "Close" and "Options." Click "Options."
16/ Choose a name for your clock from the Options menu, as well as decide whether or not to display the second hand. Note that you can also change the time zone from here.
I hope this helps