Fantastical 2 is a wonderful alternative calendar to the built in calendar app on the Mac, iPhone, and iPad. It’s amazingly intuitive, brilliantly designed, and works with your pre-existing calendar.
Fantastical 2 for Mac: http://bit.ly/fantastical2 (US Link)
Fantastical 2 for iPhone: http://bit.ly/Fantastical2iPhone
Fantastical 2 for iPad: http://bit.ly/Fantastical2iPad