Google Calendar - Spend less time managing your day & more time enjoying it
Etar - Material design open source calendar for Android.
Lightning Calendar - Organize your life — it’s about time!
Nextcloud Calendar - The Calendar app is a user interface for Nextcloud's CalDAV server.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Rainlendar - Rainlendar - Customizable desktop calendar