[@RumikoOhara]
Well, that still brings up a bit of a problem. If her people celebrate every birthday on New Year's Day, then she would actually be younger than her official birthday would say. So if she celebrates her birthday on New Year's Day, but she was actually born a few months before that, then she's one year old, even though she hasn't been alive for one year. So the way you have it has your character as officially 16 but actually only 15 and a few months. You understand what I'm getting at?