When comparing Ball O'Clock vs Calendar, the Slant community recommends Calendar for most people. In the question“What are the best custom Android Wear watch faces?” Calendar is ranked 20th while Ball O'Clock is ranked 48th.
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Pros
Pro Customizable
Colors can be customized as well as the battery indicator
Pro Animations
The animations of balls dropping and rolling and the slides rotating makes it fun to watch
Pro New concept of telling time
The concept of telling time through ball stacking is a new concept for watchfaces that makes it unique
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 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.