After being attacked by the Dementors on the Hogwarts express and then again while playing the Gryffindor vs Hufflepuff Quidditch match, Harry asked Professor Lupin to teach him the Patronus Charm.
Lupin begins teaching Harry to cast the Patronus Charm
Date January 6th, 1994
Certainty Date based on real world calendar
Location in Canon PA12: The Patronus
Type of Event Wizarding world