Pocket Informant - Pocket Informant is the Best Calendar app for mac and iOS. Pocket Informant for iOS, Mac desktop, and Android.
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Calvetica - The fast calendar for iPhone. Add an event in just two quick taps.
WeekCalendar - WeekCalendar is an all-in-one calendar application designed to provide everyone with all the features they need to work to their fullest.
Google Calendar - Spend less time managing your day & more time enjoying it
SmartDay - Integrated organizer with automatic scheduling.