I ran into an oddball issue with my wife’s iPhone 4 Birthday Calendar. The birthdays were still showing “Last Name First Name’s Birthday” (Smith Joe’s 38th Birthday) on a date in the calendar app instead of the display order that was newly set for the contacts app “First Name, Last Name.” I tried toggling on / off the iCloud calendar, the birthday calendar, sort orders and display orders. Nothing seemed to work, until I finally tried one last sequence!

If you are having problems with your iPhone birthday calendar’s display order, try this fix:

1. Close all of your apps (double-click the home screen and kill everything). It’s probably not a necessary step, but I like to work with a “clean” phone.
2. Open a contact with a birthday.
3. Change the birthday (I changed the year) and save the contact.
4. Check the calendar, your birthday calendar events now display in the proper order.
5. Change the birthday (I changed the year back to the proper one) you edited to the proper birthday and save the contact again.
6. Everything should still display properly on the birthday calendar!

I’m sure this is a rare issue, but I hope it helps anyone that runs into the problem! You can also find the discussion, where I posted this answer originally, on the Apple Support Communities Forum.