It's pretty good and understandable, but a more natural way would be: "Did you just find out about this Chinese festival, because you haven't sent me any presents in the past?" You can just say 'in the past' instead of 'in past years' as it's somewhat redundant. 'Did you just find out,' is very common way of expressing that you just learned/became aware of something: 'Did you just find out that the event is canceled?' 'Did you just find out that she broke up with her boyfriend?' 'Did you just find out that the test is next Monday?' Just a note, asking something like this could be slightly rude unless you're very good friends with the person or if it's in a semi-joking manner as it's kind of presumptuous, i.e. you expect this person to automatically be buying you gifts.

Learn or find out. "To know" doesn't usually happen at a fixed time.