birthday neighbor
Someone who's birthday is the day before or after yours
Person 1: happy birthday! I guess that means we're birthday neighbors.
Person 2: really? Was your birthday yesterday or is it tomorrow?
Person 1: my birthdays tomorrow.
Person 2: well happy early birthday, birthday neighbor.
Person 2: really? Was your birthday yesterday or is it tomorrow?
Person 1: my birthdays tomorrow.
Person 2: well happy early birthday, birthday neighbor.