Google Calendar - Spend less time managing your day & more time enjoying it
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.
BusyCal - powerful calendar app for macOS
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
iCal - In Calendar on your Mac, subscribe to calendars published or shared by others.