Windows NT 5.0 and later: An application should not broadcast this message, because the system will broadcast this message when the application changes the system time.
Windows NT 4.0 and earlier: An application should send the WM_TIMECHANGE message to all top-level windows after changing the system time.
Windows 95: An application should send 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
This message has no parameters.
An application should return zero if it processes this message.
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.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Time Overview, Time Messages, SendMessage