Xennial makes more sense for me. I was an adult in the 20th century.
I was so peeved to have a mobile phone foisted on me in 1998 so DM could keep tabs on me. It could store 8 SMS messages. Social arrangements were still very much "meet me by the statue at 7:30" because calls were expensive and SMSs could often lag. I didn't live with the internet until 2003. I began using it reguarly at school/ uni from 1997 but had to use libraries/ computer rooms/ internet cafes until then.
My music taste is more Gen X as I had an older sibling and a long memory so was exposed to their musical exploration. Plus parental music tastes. I've already outgrown Radio 2 even though I'm allegedly their target audience.
My friendships are very much late 70s- early 80s with a lot of friends securely in the Gen X band. DH is very securely Gen X, and we have a Gen X typical financial positioning. I just missed out on university grants, but the newly introduced tution fees were low. I had a bursary for my post-graduate course. My student houses were like being in The Young Ones.
I did the older style 3 A-levels before the AS/A2 split (A-level and university studies were still very much book/ journal based with limited supplimenting of online information). Y9 SATs in their limited window before they were dropped, but no y6 SATs. Y6 was an interesting school year! The National Curriculum and Key Stages had just come in and there was rearranging of school structures around that.
It was very much an analogue childhood, and while there was computing through my teens, it was niche and didn't integrate with social interactions until phones became more sophisticated in my adulthood.
The 90s/ early 2000s was such an optomistic era for teenagehood and enjoying the independence of young adulthood. It was fun and creative. You could afford to enjoy it, and there was no fear of unbridled fun appearing on social media and coming back to bite you.
A few weeks on a calendar does not a Millenial make!
Gen Xen, the best of analogue and digital.