Can someone recommend a calendar program?

[Moltke]

I use this alarm-clock-applet http://alarm-clock.pseudoberries.com/ which sits on the panel and is really usefull and does what I want. I know you asked for a calendar but it seems to me that you meant an alarm clock/system too.
You can install it via apt-get

Code:

$ sudo apt-get install alarm-clock-applet

then, right click on the panel, select panel > add new items and add the applet. Set your custom alarms and that's it. It has a timer which I think can manage what you want to do; biweekly alarms.
Hope this helps!