22 September

On 22 September 1960, Tegan Jovanka, companion to the the Doctor in his fourth and fifth incarnations, was born in Brisbane, Australia.

22 September was also the birthday of a British actor and singer named Billie. (AUDIO: The Gathering)
 * Although the radio turns off mid-sentence, this is a likely reference to Billie Piper, an actor and singer who was indeed born on this day.