Hi Steven Berger,
Welcome to Apple Support Communities! We're glad you've reached out for help with this question about birthday information in your contacts. We're glad to help!
Let's get to the bottom of this together. By default, when a birthday is added to a contact, it should appear in the Birthdays calendar in the Calendar app.
To start, please let us know more about what's going on. When you add a birthday to an existing contact, are you adding their correct birth year as well? If you don't know the year, what happens if you leave it blank? Does the birthday disappear from the contact entry after saving the changes?
Are you currently syncing your contacts with any online services, such as iCloud or Google? It's important to note that if you have contacts from multiple online accounts, there may be separate Birthdays calendars that appear in Calendar app. Also, the iCloud Birthdays calendar is updated daily, so you may not see changes in the Calendar app for a day.
Let us know if the information in this guide helps:
If your iCloud Contacts, Calendars or Reminders aren't syncing – Apple Support
Have a great day!