When comparing Lightning Calendar vs Calendar, the Slant community recommends Calendar for most people. In the question“What are the best calendar apps for Mac OS X?” Calendar is ranked 1st while Lightning Calendar is ranked 12th. The most important reason people chose Calendar is:
Calendar for GNOME aims to find the perfect balance between features and usability.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free, Open Source
Lightning Calendar (just as Thunderbird) is completely free and open-source meaning that anyone can use it as well as look through the code or even use the code for their own projects.
Pro Cross-Platform
Wherever Mozilla Thunderbird can be installed, the Lightning calendar can follow:
Windows
Linux
MacOS
Pro Easily keep track of tasks
Bundled in with the calendar options is a tasks option that makes for an easy way to keep track of tasks in the same location as ones events.
Pro Simplicity
Calendar for GNOME aims to find the perfect balance between features and usability.
Pro Synchronisation
It has online accounts integration.
Pro Currently in active development
GNOME Calendar is improved with every release cycle of GNOME.
Cons
Con Available only as part of Thunderbird
No standalone version of the calendar app is available. And if you're just interested in Lightning Calendar and not Thunderbird, the app will have additional functionality and interface elements that will get in the way of using the calendar.
Con Does not always clear old events from the display, even when the event has been deleted
When accessing Google Calendar, every check shows that the event does not exist anymore.
Con Not to all the versions
I had to downgrade my Thunderbird just because Lightning didn't upgraded to the last beta version....and I can't live without Lightning.