Assign a custom date to a custom label for a contact

Question

I have an application that for some reason should set a custom date for user contacts. The application was disconnected and worked fine. Now I want to create a quick version of the application.

When testing on xCode 6 iOS7 + 8, everything looks great, but when testing on the device, I see that the date is added as the user's anniversary date and without my custom label.

I tried to add the date directly to the native contacts application and found that new contacts are not able to add a custom date.

Testing for Yosemite I still find this option available.

While checking the ABPerson API, I found that the API still has kABMultiDatePropertyType

// Dates
AB_EXTERN const ABPropertyID kABPersonDateProperty;              
// Dates associated with this person - kABMultiDatePropertyType

It is important to note that when saving a new date, I do not get any errors and the date is saved, but without my custom label, which is important because I do not want to redefine the user's anniversary date.

Any idea why this is happening / any workaround?