Honesty, a callendar app is one of most important app for me. I am freelance photographer so I need to know during the shooting next available days for second shooting etc.
Alsom im big fan of google calendar, for example I can see in month view 2–3 days long task which in classic osx Calendar Ican not.
So my next go to app is called "Calendars". I have month, week and view similar to google and my favorite, list view.