Rainlendar - Rainlendar - Customizable desktop calendar
Simple Calendar - A simple calendar with events (optional recurring and reminders), week numbers and a customizable...
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
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.
Date Reminder - Date Reminder reminds you of recurring or nonrecurring events, like birthdays, bills to pay...
GMinder - GMinder is an open source Windows System Tray app that pops up to remind you about Google Calendar events.