WM_TIMECHANGE
wParam = 0; /* not used, must be zero */
lParam = 0L; /* not used, must be zero */An application sends the WM_TIMECHANGE message to all top-level windows after changing the system time.
This message has no parameters.
An application should return zero if it processes this message.
Any 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_BROADCAST.