Google Calendar - Spend less time managing your day & more time enjoying it
Simple Calendar - A simple calendar with events (optional recurring and reminders), week numbers and a customizable...
Lightning Calendar - Organize your life — it’s about time!
Morgen.so - All-in-one Calendar, Tasks & Scheduler. Morgen is the single hub for everything that revolves around time management.
GMinder - GMinder is an open source Windows System Tray app that pops up to remind you about Google Calendar events.
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.