1. On your domain controller, add a new attribute that is a Case Insensitive string. You can name it whatever you like. I'm naming mine NewHireDate.
If you don't know how to add attributes to AD see this article:
2. Enter in the hire date for the user in AD. I'm entering 11/26/2018
3. Edit the web.config file on the webserver and add the new field name you created in AD. Mine is NewHireDate
4. In Profile Field Manager change provider to Active Directory, set Field Name to the field name you created. Mine is NewHireDate.
5. Under Module Tools > Portal Framework > Module Properties. Change HireDateFieldName to the field name you created. Mine is NewHireDate.
6. Make sure to Recycle your Application Pools for the Portal on your server within Internet Information Services
Now the correct anniversaries should show up on the anniversary island.