We do birthdays (when we remember) at our house, not Gotcha Days. Never heard of Gotcha Days, until a few years ago. Not going to change my habit now. lol
The date is chosen by the first vet visit and the age the vet thinks the pet is.
Misa's first vet visit (rescue took her) was March 15 of last year. Vet guessed her age at 3.
Soooo, she was officially 4 years old on the 15th.