Kimmo,

Is there any (easy) way of intigrating the calender into the Ubuntu taskbar in the same way as it is in Windows?

In Ubuntu, I can't see if the calender is active or not. I have to minimize all windows to find my calender. Where as in Windows, there is a seperate icon next to the clock containing the day of the month (which is great!), and if I click once on that icon, the calender appears
In Ubuntu there is nothing, just an active calender which always disappears whenever when I open a few new Windows

If you could change this, that would be really great!

Thanks in advance.

That zone of the taskbar is called tray, system tray (or systray) or tray icons.
See if this post helps you: www.rainlendar.net/cms/index.php?option=com_kunena&Itemid=42&func=view&catid=3&id=16617#16619

That was the solution, thank you.
Also, I had to enable the systray icon manually in the settings afterwards.