On any given month, sometime will probably notice a Nintendo Easter egg. They're so good about putting little homages into their work, including this small, useless functionality.
Evidently you're allowed to enter through "1889" as your date of birth when creating a Nintendo account, which naturally circles back to their origins as a card company in Kyoto Japan.
It's not something that's going to change your life, but it did bring a smile to my face. In case you're wondering, the oldest living human of all time was 122 years of age, which would have been eligible seven years ago.
Earliest year you can put in when signing up for a Nintendo account [Reddit]
via destructoid https://www.destructoid.com/nintendo-accounts-allow-a-birth-date-of-1889-as-an-homage-to-the-company-485492.phtml