Ash Ketchum's Birthday Today! | Bulbagarden

The date of Ash's birth, according to Takeshi Shudo's anime novelizations, is 10 years, 10 months, and 10 days exactly prior to the day he began his Pokémon journey. Being that the same novelization declares that Pokémon Trainers obtain their first Pokémon in April of the year following their 10th birthday, and the anime itself began broadcast on the first of that month in 1997 in Japan, Ash's birthday, if April 1 was the first day of his journey, would be May 22.