When comparing Lightning Calendar vs Fantastical 3, the Slant community recommends Lightning Calendar for most people. In the question“What are the best calendar apps for Mac OS X?” Lightning Calendar is ranked 12th while Fantastical 3 is ranked 16th. The most important reason people chose Lightning Calendar is:
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.
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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 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 Cross-platform
Wherever Mozilla Thunderbird can be installed, the Lightning calendar can follow:
Windows
Linux
MacOS
Pro Amazing usabiliy
It has a neat design and gives a great overview on events of a day. Adding and removing events is easy.
Pro Joining Conferences via context menu or hyperlink in event on calendar
You are late and you have to join a call, you want to be fast.
Pro Integration of Google Meets when creating events
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 No full CalDAV support
CalDAV support is more hackish than working reliably. E.g. certain fields are not supported, or alarms can lead to duplication of events or changes being reset. As CalDAV support is not truly built-in, and the extension does not have a high quality.
Con Requires third-party gmail integration
And it's not supported in 60+. Use the old versions if you want anything to work.
Con Not for all the versions
You have to downgrade Thunderbird just because Lightning didn't upgrade to the last beta version.
Con Long term availability/ support
Although Thunderbird has an impressive track record and many years of reliable service, its continued existence has been doubtful more than once). For now, all seems good, but it would not be surprising if tomorrow it turns out Thunderbird "has left the building".
Con GUI makes you feel like it's 1995, and not in a nostalgic way
Con Yearly subscription
Even though you might also use cardhop, subscription based models are unpopular.