Calendar Apps that Show "Other" Dates from Contacts

I cannot find a solution to this calendar-contacts issue, so I am writing to seek guidance from the TidBITS community.

Do any iPhone calendar apps tap into yearly dates that exist in our Contacts app entries – other than birthdays and anniversaries?

The default Apple Calendar includes the ability to show Birthdays on the calendar. BusyCal includes the additional option to Show Anniversaries Calendar.

But do any calendar (or alternative) apps have the ability to show all the other annual dates preserved within Contacts? This could include a friend’s child’s birthday within the friend’s contact card. Or the anniversary date of a relative’s death within their contact card. Or the birthday of a colleague’s pet rabbit, Fluffy, within the co-worker’s contact card.

The iPhone Contacts app lets users input other dates, but the information seems to just sit in obscurity. Are there any apps that provide the ability to publish those other dates into calendars?

I can’t help, sorry. I do want to thank you for posting this, because I hadn’t known that I could add an anniversary or other date to a contact card. I had just been doing it in the contact notes.

And I don’t mean to derail the thread, but does anyone know how to get Contacts to honor the system settings for date format? Nothing I can do will budge it off mmmm d, yyyy.

Just noting that Fantastical can also show anniversaries in both macOS and iOS, but I’ve confirmed that it cannot show “Other” dates.