Anti-Virus Software Doesn't Recognize Daylight Saving Time

Anti-virus programs often record and check time stamps of important files. Under Windows NT, the time stamps of files change by one hour during daylight saving time. This may appear as a problem to an anti-virus program that doesn't take daylight saving time into account.

When you change to or from daylight saving time, time stamps of your files change by one hour to account for those that don't use daylight saving time. An anti-virus program that does not keep track of daylight saving time does not adjustment its time table.

To explain why Windows NT does this, here's a quick example. Say you were comparing the time of two files, X and Y. You want to make sure that file Y is always up-to-date, and Y depends on X. So you update the information in Y when X has changed. (NOTE: This is often used in programming project management to make sure that your executable is up-to-date by comparing it to its source.) If X and Y existed in two different locations, one that observes daylight saving time and another that does not, you might run into a problem comparing the time values. If the time doesn't change, then the information in Y could be updated prematurely.

If you want to change the clock manually:

1. In the Control Panel window, choose the Date/Time icon.
2. In the Date/Time dialog box, clear the Automatically Adjust for Daylight Saving Time check box.

The time stamps of files aren't affected when you manually change the clock.