An application sends the WM_TIMECHANGE message to all top-level windows after changing the system time.
WM_TIMECHANGE
wParam = 0; // not used, must be zero
lParam = 0; // not used, must be zero
Parameters
This message has no parameters.
Return Values
An application should return zero if it processes this message.
Remarks
An application that changes the system time should send this message to all top-level windows. To send the WM_TIMECHANGE message to all top-level windows, an application can use the SendMessage function with the hwnd parameter set to HWND_TOPMOST.
See Also