Software to power an online events calendar

I'm currently looking for an online calendar for our portal. Most events need to be added online by event organisers themselves in a content management system throughout northern Germany etc. We may consider an extra news page option, which could be used, for example, to report on the events afterwards and allow users to add sport results.

Sub calendars
User databank
Sign in: Password and User managment
Online event alerts
Recurring events
Flexible settings and control
Definable events categories
Public & private calendars
Export to vCal, eCal formats
Advanced search capabilities
System backup
British date format
24 hour clock, not AM PM
Adaptable design, size colours and backgrounds
One extra calendar homepage, with smaller box/display on normal homepage and existing events page
Possibly PHP based
English language - possibly mixed with German

Any suggestions that do not cost the World (with receipt for tax purposes), or freebies welcome!
I am currently redesigning the portal, so if anyone needs a preview of the portal, to see how to adapt to the design, let me know.

Thanks in advance!

http://www.teamkalender.com might do some of this.

My favourites so far are:

http://www.toronto.com/events - the way they designed it...
http://www.web-site-scripts.com/web-calend...creenshots.html - the software itself, only if it can be adapted.