Google Calendar - Spend less time managing your day & more time enjoying it
24me - Next Generation Personal Assistant
BusyCal - powerful calendar app for macOS
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.
Calvetica - The fast calendar for iPhone. Add an event in just two quick taps.