Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Clocks - A minimal world clock app for your Mac's menubar
BusyCal - powerful calendar app for macOS
Spacetime - Work hour and time zone management for distributed teams.
Google Calendar - Spend less time managing your day & more time enjoying it
Every Time Zone - Online tool for keeping up with times around the world.