iBirthdayCalendar on iPhone:

Ever wish you had all birthdays in one place? Here’s your chance. Birthday Calendar will help you track all those special days in your life.

With this free app you’ll never forget any birthdays by:

– View upcoming birthdays with age, zodiac, photo and countdown in a calendar format;

– Import birthdays from iPhone contacts & Facebook by one-click;

– Publish birthday countdown to Facebook or send it by mail;

No need for more description. Intuitive UI and operations make it so handy. Why not have a try?

Available at iTunes Store: http://itunes.apple.com/us/app/ibirthdaycalendar/id367346406?mt=8

Screenshots and User Manuals:
1. In default view, you will see your friends’ photo, name, birthday, age, zodiac and category (from Facebook, from iPhone contacts, or created by iBirthdayCalendar). You can also see the countdown to next birthday in rightmost column:

2. By switching to calendar view, you can see all above information categorized into different date sections:

3. You can add a new birthday by clicking “+” in toolbar. You can pick up a friend from iPhone contact, and if you choose “Update birthday to contacts”, the new birthday will also be recorded into this contact in your iPhone address book. If you don’t know exact year when your friend was born, switch off “Known Birth Year”:

4.  You can import friends from Facebook or iPhone contacts. Important: re-importing will replace all your existing imported birthdays in this category (facebook or contacts) with new imported ones.

5. You can view details for each birthday, you can edit the birthday in this page and publish birthday countdown to Facebook or email:

6. Edit/Delete a birthday:

Currently you cannot rename a contact but you can delete it then add it again.

To delete a contact, just follow default iPhone table row delete scheme:

Delete button: Users tap this element to delete the list item. This element appears to the right of a list item when users swipe in the row or when they tap the delete control button while in an editing context. 
From:http://developer.apple.com/iphone/library/documentation/UserExperience/Conceptual/MobileHIG/ContentViews/ContentViews.html

In the coming update, a “Delete this contact” button will also be added in “Info” view, this will be more intuitive.