Simplish - Simplish is a day planner software that is used for time management.
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
CiraSync - CiraSync is a program that syncs and shares office 365 GAL contacts and calendars to smartphones.
BusyCal - powerful calendar app for macOS
Clariti.app - Clariti is a team communication app that uses Artificial Intelligence to combine emails, chats, documents, calendar events and feeds on the same topic, in rich context-based Conversations to ensure your communication stays focused & organized.
Google Calendar - Spend less time managing your day & more time enjoying it