So I found this cool book online called Disneystrology. It has everyday of the year paired up with a Disney character. So you find the date of your birth, and it explains how you are like that certain character. It included some Pixar characters in the book, so maybe this is the closest thing to their birthdays? Here is a list of the dates with Pixar characters…
January 1st- Jack-Jack Parr
January 4th- Carl Fredrickson
January 16- Doc Hudson
January 20-Lizzie
January 24- Buzz Lightyear
January 28- Flik
February 2nd- Captain B. McCrea
February 6th- Woody
February 7th- Fillmore
February 10th- Boo
February 11th- Remy
February 20th- Dim
February 21st- Red
February 23rd- Elastigirl
March 19- Nemo
March 22nd- Dash
April 7th- Lightning McQueen
April 9th- Bubbles
April 14th- Princess Atta
April 15th- Gusteau
April 24- Mack
April 25- Heimlich
April 30th- The Queen
May 3rd- Sheriff
May 13th- Rosie
May 15th- Tuck and Roll
May 20th- Russell
June 1st- Gypsy
June 3rd- Dory
June 7th- Tia and Mia
June 10th- Jessie
June 11th- Mr. Soil
June 19th- Dot
June 23rd- Dug
June 26th- Mr. Incredible
June 28th- Mater
July 4- Sarge
July 5th- Andy
July 8th- Django
July 19- Frances
July 25th- Luigi
July 28th- The King
August 2nd- RC
August 14th- Rex
August 16- EVE
August 19th- Kevin
August 22nd- Ellie
September 9th- Linguini
September 10th- WALL-E
September 12th- Gill
September 13th- Wheezy
September 17th- Dr. Flora
September 18th- Rick Dicker
September 20th- Sally
September 26th- Roz
September 29th- Sulley
October 2nd- Hamm
October 9th- Celia Mae
October 10th- Emile
October 26th- Colette
October 28th- Edna Mode
November 3rd- Violet Parr
November 6th- Manny
November 10th- Marlin
November 12th- Flo (Cars)
November 13th- Peach
November 16th- Karri
November 20th- Mike Wazowski
November 25th- Guido
November 30th- Nigel
December 1st- Bo Peep
December 3rd- Ramone
December 9th- Frozone
December 12th- Slim
December 14th- Mr. Ray
Did this help?