I provide Joomla! solutions for German NGOs and use DPCalendar as my favourite at the moment. For my customers it is easy to use, for me it is easy to adapt the existing design (very good code structure). Anyway, I love this extension because I can just use it as a native Joomla! extension. Moreover it comes with powerful features to import external calendars like google, ical and so on. I've posted two threads into the developer's forum and got a very fast and helpful reply. Thank's a lot for this mighty feature and your good support!