Follow the instructions on this page to install islamiccal.

Java 1.6 and itools will be installed with this package.

Try launching it by typing in a terminal (Applications→Accessories→Terminal):

islamiccal

If you have this kind of error:

Launching Islamic Calendar...
Exception in thread “main” java.lang.UnsupportedClassVersionError: Bad version number in .class file

or:

Launching Islamic Calendar...
Exception in thread “main” java.lang.ClassFormatError: ubuntume.islamiccalendar.IslamicCalendar (unrecognized class file version)

Type the following command:

sudo update-alternatives --config java

and select “/usr/lib/jvm/java-6-sun/jre/bin/java”.

Islamic Calendar will be executed automatically at startup.