Hi Bystrik,
I don't have a calendar you can use but I can point you towards needing the Canvas Object for how to achieve it.
We do have a calendar and use one canvas item for handling the movement of months, days etc and then another canvas object for the main central bit (ours is several people for a day rather than several days for a person).
The main things to bear in mind are:
1) You only have 1000 x 1000 pixels in any given object (though can have lots of objects)
2) I can't work out how to resize text away from the default
3) You need to use some undocumented stuff to handle the function keys. You set a single F-key as a left click and a single F-Key as a right click then (for example) 'COMMAND KEY (F92)' and then use the undocumented features to identify the object clicked (actually very straight forward).
See the attached image