I run a JAVA application on the X without a window manager. Just plain application using a touchscreen to navigate. Everything works fine until I change the date with the date command to some time in the future and then to some time in the past. The GUI does not update the screen anymore after those date commands. I thought it might be a JAVA problem and tried the same commands on a system running a GUI written in C.
I got the same result the GUI freezes the meters and cannot be navigated properly anymore, although it reacts to a mouse click. It looks like that the
mouseclick wakes it up for some milliseconds and freezes it again.
When I access the GUI from remote with VNC it works ok but the local GUI
remains in a frozen state. The GUIs run on a Redhat9 and a Mandrake 8.0,
but that makes no difference to the problem.

this is a standard problem with X and the kernel, every time you start an application, linux logs the time it was started, it also looks at how long applications have been running.

to fix this problem, you will need to press Control+Alt+Backspace to restart an X server

this will close any open applications, but it will restore functionality to your X server