iOS: Agenda is a minimalist, elegant calendaring application that we've highlighted before. The developer recently updated the application to include an iPad version, and has improved the iPhone version to make editing calendar appointments easier.
The app retains its minimalist appearance, but the iPhone version now allows you to edit an event by tapping it in event view, and on the iPad there's now a persistent "Edit" button available across multiple parts of the application. The new iPad version looks and operates like its iPhone cousin, and offers a clean, one-glance view of all of your appointments and events for the upcoming day, week, or month, if you choose. The app also makes it easy to switch views with a single tap.
Agenda is available in the iTunes App Store now for $0.99, and because it's universal, you can buy it once and use it on the iPhone and the iPad.