Welcome to the forum Kato40. I hope You will enjoy Your time here.
Are You using KDE3 or KDE4?
Open any K[application] and Click Help > About KDE to see what version are You running.
If You are using KDE4 than I think that the package that You want is called
Install it via Synaptic Package Manager
. Then right click on the desktop and choose Unlock Widgets
. Right click again and choose Add Widget
Find widget named World Clock
and double click on it. It will appear on the desktop. You can play with it then. Drag
it to move it around. Use the tools on the side of it (it pops out when You move mouse above the widget) to resize
it and Right Click on the Widget to get extra option
Hope this helps.