Sunrise Calendar is a solid alternative for the default iOS calendar app. In addition to looking good, it also offers additional features you can't find in Apple's Calendar app.
By connecting your Facebook, Google, and iCloud accounts, Sunrise is able to bring together all of your calendars. With appointments that have fellow attendees listed, you're able to view information about the respective person directly within the app.
In an effort to bring even more of your calendars under its domain, Sunrise recently released an update that allows you to add "more than 25,000 calendars for holidays, sport teams, name days, week numbers, and more" per the change log in the App Store.
So instead of having to search through Google's database for a calendar someone else has created, Sunrise has streamlined the process and made it easy to add a special calendar directly from your iOS device.
To browse and add one of the new calendars, make sure you're running version 2.3 of the app.
Then, from the main screen, tap on the Settings icon in the top-left corner.
After scrolling down past your personal accounts, you'll find a listing for Interesting Calendars; tap on it.
You can now browse through and search the numerous calendars Sunrise has incorporated. The addition of interesting calendars is a nice touch to an already well thought-out app.
To edit any of the interesting calendars, go back to the settings and tap on the Interesting Calendars section, followed by Edit.