Google Calendar is a pretty slick thing these days, especially as part of the wider integrated ecosystem of your Google account. With helpful reminders linked to Google Now and the ability to create appointments based on your emails, you don't really have any excuse for being late anymore.
And now you can do most of the same things on iPhone, with the new Google Calendar app for iOS.
It's an official product straight from Google which will allow you to easily move from your desktop or tablet to an Apple device without leaving behind your Calendar entries. It integrates with Gmail (provided you have one) and wll bring together existing calendar entries from other services like Exchange and iCloud. It's likely not quite as fully featured as the app on a native Android device, for example it may not work so well with Google Now or voice controls but the sharing across different operating systems by rival companies is never a bad thing for users.
Grab the Google Calendar app for iOS here right now.