CiraSync - CiraSync is a program that syncs and shares office 365 GAL contacts and calendars to smartphones.
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Simplish - Simplish is a day planner software that is used for time management.
Google Calendar - Spend less time managing your day & more time enjoying it
Socialsuite - Impact measurement with measured outcomes
Itsycal - Itsycal for Mac. Itsycal is a tiny menu bar calendar. If you want, it will display your events as a companion to the Mac Calendar app. You can also create and delete (but not edit) events. Download Itsycal for macOS 10.