good example to learn about plugin development

This example helped me a lot with the basics of plugin/widget development. The times for sunset/sunrise etc. are retrieved by calling a web service. I later found out that (depending on the php version available) the data can be calculated using the built-in function date_sun_info i.e. without the need to call an external web service. Implementing the aforementioned date_sun_info instead of the web service is simple.