Flexibits has released Fantastical 2.3.4, adding support for Google’s new login requirements and improving performance for very large calendars. The popular calendar app now enables you to create events that repeat every month on the 1st through 20th weekday (for iCloud, Google, and other CalDAV accounts). It also lets you ignore all pending invitations by pressing Option while right-clicking on an invitation. The update improves launch time with large numbers of birthdays from Contacts, fixes a bug that caused some recurring events to repeat incorrectly, avoids a crash when replying to Facebook events, and resolves an issue with the app not launching on OS X El Capitan 10.11 through
10.11.4. For a limited time, Flexibits is celebrating Fantastical’s birthday by putting the app on sale for $39.99. ($49.99 new from Flexibits and the Mac App Store, free update, 14.0 MB, release notes, 10.11+)
Can't find any upgrade route from V1.x of Fantastical.