How Windows keeps track of the date and time

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This article describes how Windows keeps track of the date and time.
When you start Windows, it gains direct access to the memory of the Real Time Clock (RTC) and uses its date and time values to set the computer date and time. Timer interrupts maintain the computer time when Windows is running. A Time Daemon in Windows runs approximately once each hour after the Windows starts. The Time Daemon compares the time in Windows with the time in the RTC. If the two times are more than one minute apart, Windows changes the time and date to match the RTC. You cannot change the time interval for the Time Daemon to run.

If you use a time synchronizing service, such as the TimeServ.exe tool included with the Windows NT 4.0 Resource Kit, the tool updates the time in Windows and the computer's RTC.
If the Windows Time Service runs on a Windows 2000 based-computer, the Time Daemon in Windows cannot run approximately one time each hour after the Windows starts.
For more information, visit the following Microsoft MSDN Web sites:
time, RTC, BIOS

Article ID: 232488 - Last Review: 12/05/2015 14:38:47 - Revision: 3.2

Microsoft Windows NT Server 4.0 Standard Edition, Microsoft Windows NT Workstation 4.0 Developer Edition

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