I don't know about you, but I've never been a big fan of the iPhone or iPad's built-in calendar. Don't get me wrong, they're serviceable but they lack the features of some of the calendar apps that are out there.
Around the first day of getting my iPhone 3GS, I found a calendar app by Utilitap that had a lot of awesome features that the native iOS app lacked: different calendar views; color coded calendars; holiday/birthday displays; drag and drop; custom event templates; recurring events (this is a robust feature); custom event icons; auto colors/icons; calendar syncing across multiple services, etc. It's also a well-designed app that is incredibly simple to use.
Did I mention it's called Week Calendar (aka Week Cal)?
Once upon a time Utilitap had released an iPad version of the app called Week Calendar HD, but for some reason, Apple wound up removing it from the App Store, before I had a chance to download it and I was unfortunately stuck with the native iOS calendars app. In the past couple of months, I finally reached a point where I needed something better and I downloaded Readdle's Calendars app – a very good looking app with a little more functionality over the native app, but it still lacked the features of Week Cal.
I have learned that Utilitap has released a new and improved Week Calendar HD, passing Apple's stringent guidelines, for iPad. It has all of the great features of its iPhone app as well as a sync option, for syncing settings and templates via the cloud to multiple devices. Awesome. The app was rebuilt from the ground up and is gorgeous, making full use of the iPad's size.
The one downside is that there isn't a universal app for both iPhone and iPad, requiring a separate purchase. However, both versions are very much worth the modest price they charge, especially given all of the great functionality the apps add to your device(s).
As of this writing, the iPad app is $2.99 in the App Store.
You can read more about the announcement here: http://blog.utilitap.com/2013/03/press-release-top-productivity-app-week.html
You can learn more about both apps at the Week Cal website: http://www.weekcal.com/