Earlier quoted context omitted.
It's not that weird - I'm sure most folks spend their school-years referring to other kids as "the same year (grade) as me" or "the year (grade) above/below me". Even to this day, I intuitively group friends based on the academic year group they were in.
> Even to this day, I intuitively group friends based on the academic year group they were in How far out of school are you?
People from my year are the ones I lived with, did group projects with, worked until midnight trying to solve a difficult task that had been set, celebrated the last exam with, etc.
I certainly don't know the year for everyone. Students I mostly saw at parties, who studied different subjects (or went to different universities, for it was London) could easily be my year ±3 or more.