There's certainly no shortage of great calendar apps for iPhone, but it can't hurt to try something new like Peek Calendar. On the surface it looks pretty simple, but there are some neat things under the hood.

Tap on any given calendar date to "unfold" the list of events for that day, or hold on a date to create a new event. From there, tap and drag various elements to set the time and length of the event. Hold your hand over the top of the iPhone to "shade" its light sensor, and a shadow will appear on-screen that displays the current time. You can get a feel for everything the app does by watching their promo video.

Peek Calendar is only $2 on the iOS App Store.