Calendar Hub od Eniac Labs Inc.

Calendar Hub puts every calendar you use side by side in one clean, read-only view.

Connect several Google accounts (work, personal, family) and see them together
Add any calendar by link: Outlook, iCloud, Proton, Fastmail, Nextcloud, school and sports schedules, or Google's "secret address in iCal format"
Day, week, month and agenda views with a filter box
Toolbar popup and badge showing your next event
Merges duplicate invites, hides events you declined, colors by account or calendar
Light and dark themes