I just tried wmCalendar without Internet and it seems to work. So basically it seems the problem is in my code ... ?
-edit- its a bit more complicated. It turns out for my use case I indeed need internet
So my use case:
The user creates an appointment with third party app google calendar.
User returns to my app and wants to reference this appointment.
Now if the user has no internet, wmCalender delivers a list of appointment, however this event that was just created is not contained! ...
So basically there is internet connection needed for Google Calendar to upload the appointment. Once it is uploaded Google Calendar can also provide this event offline.
This sounds weird but I just tested it ...