Right/left
But when I was younger all the way through middle school I would wear it on my right wrist
My mom, who is ambidextrous (but still favors her RIGHT hand) wears her watch on her right wrist. That's partially b/c my grandma is left handed (and wore her watch on her right wrist)... Fun fact: My grandma taught herself to knit left handed by watching someone who was right-handed do it and then she reversed the technique.