Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
BusyCal - powerful calendar app for macOS
Meeter - Hop in and out of calls, directly from your menu bar
Google Calendar - Spend less time managing your day & more time enjoying it
Superpowered - Power through the day without your calendar
iCalBuddy - iCalBuddy is a leading command-line utility that can be used to achieve a list of tasks and events from the OS X calendar database.