DOC: Obtaining System Time Using KeQuerySystemTime

ID: Q239818

The information in this article applies to:

Microsoft Windows NT 4.0 Driver Development Kit (DDK)

SUMMARY

The Kernel-Mode Drivers Reference included with the Microsoft Windows NT DDK 4.0, Part 1: Kernel-Mode Support Routines, Chapter 5: Kernel Routines, Section KeQuerySystemTime, states the following:

KeQuerySystemTime obtains the current system time.

Parameters
CurrentTime

Points to the current time on return from KeQuerySystemTime.

Comments

System time is a count of 100-nanosecond intervals since January 1, 1601.

This function obtains the current system time maintained by Windows NT. The system clock holds the system time in units of 100-nanoseconds, but has an update period set by the system timer interrupt. This is typically around once every 10-milliseconds. In a Uniprocessor HAL, an increment value of approximately 100,000 (100000 x 100-nanoseconds = 10 milliseconds) is added to the system time for every timer interrupt.

MORE INFORMATION

The exact increment value can be obtained by using the KeQueryTimeIncrement function.

REFERENCES

Please see the Windows NT Device Driver Kit documentation for additional information on KeQueryTimeIncrement

Additional query words:

Keywords : kbdocerr kbDDK kbNTOS400bug kbDSupport kbGrpNTDDK
Version : winnt:
Platform : winnt
Issue type : kbbug