When is Jason grace's birthday in the lost hero?

Jason: blonde hair, blue eyes, age 15, last name Grace, brother of Thalia Grace, son of Jupiter (zeus)

Piper: brown hair in two braids, (unknown eye color), age 15, last name McLean, daughter of Aphrodite

Leo: Black hair, age 15, last name Valdez, we find in the son of neptune that he's known to Hazel as her old boyfriend, sammy valdez. son of Hephaestus.