Well, it’s weird you had to look it up since it gave her birthday in the screenshot twice, once in massive text, but my initial point I was gonna make was she’s just an older emo kid. She’s older than I am, but close to my older siblings age, I was an emo middle school kid while they were in high school. They weren’t emo, but they were the perfect age for it. She just never grew out of it. She’s an OG scene girl. “E-girl” is just the modern take after white people got into manga.
The 400 year rule is the reason it was a leap year. Every fourth year is a leap year except if its divisable by 100 but not 400. 1900 wasnt a leap year but 2000 was. 2100, 2200, 2300 will not be leap years but 2400 will be one.