When comparing KOrganizer vs Calendar, the Slant community recommends Calendar for most people. In the question“What are the best calendar apps for UNIX-like systems?” Calendar is ranked 1st while KOrganizer is ranked 5th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Multi-category
Pro Long-time support
Pro Integrated into KDE
It can be used by clicking on the datetime in the bottom right corner.
Pro Imports well from Google Calendar
Pro Easy and intuitive to use
Pro GNOME native integration
Pro Currently in active development
GNOME Calendar is improved with every release cycle of GNOME.
Pro Simplicity
Calendar for GNOME aims to find the perfect balance between features and usability.
Pro Synchronisation
It has online accounts integration.
Cons
Con Search events by text shows empty results for existing events
Con Has issues with recurring events with exceptions
Has trouble with recurring events that have exceptions to them. If recurring even has an exception to the pattern at some point KOrganizer seems to not display any of the recurring events. Thus making it useless for complex calendars. After verifying that the akonadi back end did have the full set of events, KOrganizer just does not interpret them correctly.
Con Does not connect to secure CalDAV server
Con Does not connect to Fastmail
Con Crashes even whilst trying to launch the app
Con Crashes when trying to add new event
Con Requires KDE
Con Cannot print
Con Extremely buggy
Con Poor interoperability with online calendars
Does not connect to Fastmail.
Con Far too simple
Con FAR too tied into the GNOME infrastructure
The UI and configuration presume you are running GNOME, and has the ugliness of a GNOME application. Configuration, as is usual for any GNOME application, is pretty much nonesistent.
Con Can't read 'all-day' events with dark theme
Text is white on light blue with dark themes. The workaround: assign all-day events to just one hour.
Con Can't import ics files
Con Continues to pop-up reminders that are turned off and they cannot ever be removed
The GNOME Calendar displays pop-ups from an old Google Calendar that was used. That Google Calendar has long since been removed from GNOME, and even with the notifications turned off on the GNOME Calendar, the pop-ups still happen.
Con Incorrect appointment times when importing .ics calendars
Con No support yet for WebCal
No support yet for WebCal, such as those offered by Facebook events.
A workaround exists. Since this application uses the same background services as Evolution, installing it and adding the WebCal calendars there, also adds them to GNOME Calendar.