This question already has an answer here:
Simple question: I read that the axial tilt of Uranus is 97.77 degrees. I don't understand why it would be this instead of 82.23 degrees the other way. It seems like saying that the Earth's axial tilt is 157 degrees rather than 23, or something. can someone explain why Uranus's axial tilt is bigger than 90 degrees?
EDIT: this is not a question of how it came to be so tilted, I am sure that is answered elsewhere, but simply why it is accepted as being bigger than 90 degrees rather than less than 90 degrees the other way. it is the same for Venus.