see chronology of the harry potter stories for more information on the timeline in a nutshell it is based on a comment by nearly headless nick in chamber of secrets when he invites harry to his th death day party and mentions he died oct so if it is his th death day chamber of secrets takes place in harry's nd year at hogwarts when he was since he had to be to enter hogwarts as mentioned in philosopher's stone therefore harry's birth year was since luna and ginny are both a year behind their birth years are voila