When is their birthday?

Birthdays are on my brain.    Everyone has one and they come very year at the same time so why is it I can't remember Ollie's?    He's the only animal we own where we actually did know at one point many years ago...his true and honest day of birth.     He was purchased from a bug eyed lady in Lancaster  Texas and brought home to Pflugerville when college girl was 5.   So he's now 14?  because she is now 19 and born on Nov. 2 1990.  Yesterday was her birthday...hence...birthday on the brain.    Or is he 13 because it was in Feb when we brought him home and she is Nov?
Bartie was an adoptee as is Mattie.    So do you go by their adoption days/months?
To solve my problem I am giving every pet a new birthday.   I think it will help me as they and I age. Beginning this year...every pet in my house gets one year older on Thanksgiving.   I am thankful always for my doggies.     They make me smile and laugh and cry sometimes too...(really cool chewed up Bolle shades).

So on Nov. 26...Thanksgiving Day... Mattie will be 1, Bartie will be 12 and Ollie will be 14.    It's simple, easy and they really don't care as long as the snacks keep coming and their tummy gets a rub.   AND it's easy to celebrate.   There's a table full of possible treats and snacks already prepared.

Happy Birthday College girl.   You can keep Nov. 2 'cuz I was there ( with eye shadow  and good hair) and it's a day I won't ever forget!