Gnome Hebrew calendar applet
Using Linux as a computer OS, I looker for a simple and user-friendly program for displaying Jewish dates.
Google helps as usual and I found HDate applet for Gnome.
Ubuntu has it in main repositories.
$ sudo apt-get install hdate-applet
Unfortunately, not everything is so good as we want. Seems that development finished in February 2008. So, some issue still persist in the program.
Leave Time Zone setting value 0.00. Otherwise it will plus to current time timezone difference.