Harry Potter's first birthday took place on 31 July, 1981. After Harry received his first and only toy broomstick from his godfather Sirius Black, his father, James, said he was a natural-born Quidditch player.
Later, Lily Potter sent Harry's godfather a thank you letter, which also described the deaths of the McKinnons and "Wormy's" expression.
In 1997, both Harry and Severus Snape read this letter of Lily's. Harry did not read the second page of the letter until 1998.