GetSystemTimeAdjustment

The GetSystemTimeAdjustment function determines whether the system is applying periodic time adjustments to its time-of-day clock at each clock interrupt, along with the value and period of any such adjustments. Note that the period of such adjustments is equivalent to the time period between clock interrupts.

BOOL GetSystemTimeAdjustment(
  PDWORD lpTimeAdjustment,  // size, in 100-nanosecond units, of a 
                            // periodic time adjustment
  PDWORD lpTimeIncrement,   // time, in 100-nanosecond units, between 
                            // periodic time adjustments
  PBOOL lpTimeAdjustmentDisabled
                            // whether periodic time adjustment is 
                            // disabled or enabled
);
 

Parameters

lpTimeAdjustment

Pointer to a DWORD that the function sets to the number of 100-nanosecond units added to the time-of-day clock at each periodic time adjustment.

lpTimeIncrement

Pointer to a DWORD that the function sets to the interval, counted in 100-nanosecond units, between periodic time adjustments. This interval is the time period between a system's clock interrupts.

lpTimeAdjustmentDisabled

Pointer to a BOOL that the function sets to indicate whether periodic time adjustment is in effect.

A value of TRUE indicates that periodic time adjustment is disabled. At each clock interrupt, the system merely adds the interval between clock interrupts to the time-of-day clock. The system is free, however, to adjust its time-of-day clock using other techniques. Such other techniques may cause the time-of-day clock to noticeably jump when adjustments are made.

A value of FALSE indicates that periodic time adjustment is being used to adjust the time-of-day clock. At each clock interrupt, the system adds the time increment specified by SetSystemTimeAdjustment's dwTimeIncrement parameter to the time-of-day clock. The system will not interfere with the time adjustment scheme, and will not attempt to synchronize time of day on its own via other techniques.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The GetSystemTimeAdjustment and SetSystemTimeAdjustment functions support algorithms that want to synchronize the time-of-day clock, reported by GetSystemTime and GetLocalTime, with another time source using a periodic time adjustment applied at each clock interrupt.

When periodic time adjustment is in effect, the system adds an adjusting value to the time-of-day clock at a periodic interval, at each clock interrupt. The GetSystemTimeAdjustment function lets a caller determine whether periodic time adjustment is enabled, and if it is, obtain the amount of each adjustment and the time between adjustments. The SetSystemTimeAdjustment function lets a caller enable or disable periodic time adjustment, and set the value of the adjusting increment.

QuickInfo

  Windows NT: Requires version 3.5 or later.
  Windows: Unsupported.
  Windows CE: Unsupported.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.

See Also

Time Overview, Time Functions, SetSystemTimeAdjustment, GetSystemTime, GetLocalTime