Recs.
Updated
Specs
Pros
Pro Very polished natural language text entry
Fantastical makes it really easy to add events using their superb natural language parser. For instance, an entry like "breakfast at 9am at The Diner" will be handled correctly.
In addition to their best in class natural language processing, Fantastical has awesome features such as allowing users to append "/work" or "/personal" in order to add events to the specified calendar and setting up abbreviations that will add snippets of text.
Pro Allows changing what groups of calendars are shown based on location
Fantastical 2 allows grouping calendars and changing which ones are displayed based on those groups. You can also set it up so that certain groups are shown based on your location. For example, you could have one group of calendars shown when at work and another group when at home.
Cons
Con Expensive
Fantastical 2 on a Mac costs $49.99. It will come to a total of $65 if you want to get it on an iPad and an iPhone as well.
Con Can't be trusted for long-term support
When they came out with Fantastical 2 they abandoned the Fantastical purchasers (and it wasn't as stable as it should be). When they come up with Fantastical 3 I can't trust them to not abandon those who buy Fantastical 2 like they did with the original product.
Con Fantastical 2 rendered the first Fantastical unusable
When Fantastical 2 came out, those of who paid for the previous version "Fantastical" are now unable to use it because they stopped releasing security updates, it also has multiple sign-in glitches. The only way to keep using the app, is to spend another $50 and buy a license for Fantastical 2.
Con It's no better than the calendar that comes with a Mac
May be hard to customize the calendar the way you want.
Con Forces two-factor authentication and blames Apple
Fantastical 2, the only app forcing two-factor authentication, is blaming Apple for this, even though other apps are still using iCloud with the annoying two-factor authentication.