Fantastical alternatives

Fantastical
The Mac calendar you'll actually enjoy using. Fantastical's natural language engine is expressive and intelligent so you can write in your own style. Even better, Fantastical automatically recognizes the location of your event and can even invite people from Contacts (Mavericks and Mountain Lion) or Address Book (Lion and Snow Leopard) to your event.
Fantastical alternatives are:
Sunrise, BusyCal, Tempo, Google Calendar