Simple Calendar - A simple calendar with events (optional recurring and reminders), week numbers and a customizable...
Google Calendar - Spend less time managing your day & more time enjoying it
Etar - Material design open source calendar for Android.
Calendar Lock PEA - Calendar Lock PEA is an encrypted desktop calendar with a day, week and month view. The shown calendars are never stored unencrypted on your disk, but exist only in the RAM. Platform-independent, Open Source, no installation or registration required.
Morgen.so - All-in-one Calendar, Tasks & Scheduler. Morgen is the single hub for everything that revolves around time management.
Apple Calendar - Calendar is a personal calendar app made by Apple Inc. that runs on both the macOS desktop operating system and the iOS mobile operating system.