gkrellsun is a plugin for gkrellm which can display the following:

* Sun's setting time
* Sun's rising time
* Sun's estimate time before setting/rising
* Sun's path and current location on that path
* Sun's apogee path
* As of 0.11.0:
  * Moon displayed as a full image (identical to gkrellmoon).
  * User can click on image to toggle between Sun/Moon.
  * Sun/Moon images will be toggled every X minutes (changable).
  * Moon has a tooltip with more info.

There are currently two background images. One is a static UltraViolet
image and the other is an Orange image consists of six levels of
brightness. The text color for each of the Suns' rise/set/eta times
can be set independantly. The font type and size can also be set for
all the times.

Homepage:
https://gkrellsun.sourceforge.net/
