Lightning
Open Source
Lightning App Builder is a point-and-click tool that makes it easy to create custom pages for Salesforce1 and Lightning Experience.
Rainlendar
Freemium
Rainlendar is a calendar program for Windows, Mac OS X and Linux.
Apple Calendar
Free
Calendar is a personal calendar application made by Apple Inc. that runs on both the macOS desktop operating system and iOS mobile operating system.
Org-mode
Open Source
Org-mode is an Emacs Mode for Notes, Planning, and Authoring.
Compare Kontact - KOrganizer with alternatives
Compare Lightning and Kontact - KOrganizer and decide which is most suitable for you.
Compare Apple Calendar and Kontact - KOrganizer and decide which is most suitable for you.
Compare Rainlendar and Kontact - KOrganizer and decide which is most suitable for you.
Compare Org-mode and Kontact - KOrganizer and decide which is most suitable for you.