Replacing xclock with astime
astime can easily serve as a replacement for xclock. The customization of every element of the display window allows to configure it to look exactly like xclock. Or even more. Check out the screenshot at the info page for astime (http://www.tigr.net/afterstep/view.php?applet=astime/data).
An open, cross-platform journaling program.
A scientific plotting package.