A birthday was the anniversary of someone's birth. Birthdays were celebrated by many cultures.
Romana was given an air car for her seventieth birthday. (TV: The Pirate Planet)
Ace and the Seventh Doctor went to a birthday of Bonjaxx, where they met a future incarnation of the Doctor. (COMIC: Party Animals)
The video game Happy Deathday's title was a spin on the word "birthday." (COMIC: Happy Deathday)
River Song was taken by the Doctor for her birthday to the last Winter Frost fair on the River Thames in 1814. Stevie Wonder unknowingly performed before being taken back to his original time. (TV: A Good Man Goes to War)
When Sky was rapidly grown, Clyde Langer noted her lack of birthdays, remarking it was "rubbish". (TV: Sky)
The Eighth Doctor tried to take Charley Pollard to a party to celebrate her birthday. (AUDIO: Neverland)
Hex attended a birthday party for himself at a pub, but left early. (AUDIO: The Harvest)
In an alternate timeline, the Sixth Doctor and Evelyn Smythe attended Wolfgang Amadeus Mozart's 100th birthday party in 1856. (AUDIO: My Own Private Wolfgang)
The Doctor had long forgotten his birthday by the time he had reached his twelfth incarnation, but the Master remembered it from their childhood friendship. As Missy, the Master created an army of Cybermen from deceased humans and gave control of the army to the Doctor as a gift with which he could potentially rule the universe. (TV: Death in Heaven)
Princess Clio was poisoned by her Uncle Ferdand on her fifth birthday. After the First Doctor put her into stasis, she was only awoken on subsequent birthdays, each of which was attended by an incarnation of the Doctor. (PROSE: The Glass Princess)
The Tenth Doctor first met Barnaby Edwards at his birthday party at the Shady Grove Rest Home. (COMIC: Old Friend)