Calendar class is doing strange things

[eluser]reyntjensw[/eluser]
I'm implementing the calendar from the calendar library.
Can be viewed here Event in the calendar
As you can see the 15th has an event. If you go to the next month
Calendar without an event (but see source)
There are no other events in the calendar. If you look at the source, you can see that there is 1 event, but isn't shown in the calendar. I don't understand why that is.

Check out my code

Have I made some stupid mistake?

Thanks