Installing rainlendar on ubuntu is extremely simple. Just download the file and extract it wherever you feel like.
Just double-click on the rainlendar file in the extracted directory to run it. Here’s what the calendar looks like:
To make it start up automatically when you login to ubuntu, go to System \ Preferences \ Sessions
Click on Startup Programs, and click the Add button. Use the browse button to find the directory that you installed rainlendar to, and click OK.