Calvetica - The fast calendar for iPhone. Add an event in just two quick taps.
Pocket Informant - Pocket Informant is the Best Calendar app for mac and iOS. Pocket Informant for iOS, Mac desktop, and Android.
24me - Next Generation Personal Assistant
Awesome Cal - Awesome Cal is a Calendar application for your iPhone that you can take anywhere and keep close by to monitor all the upcoming birthdays, festivities, meetings, and more from a single place.
SmartDay - Integrated organizer with automatic scheduling.
Morgen.so - All-in-one Calendar, Tasks & Scheduler. Morgen is the single hub for everything that revolves around time management.