Been interesting in this too, I’ve just found this info from BC
5.9 The following age categories and sub-categories may be
recognised in Federation cyclo-cross events:
Under 12 Up to 31st August in the year of 12th
birthday.
Youth From 1st September in the year of
12th birthday to 31st August in the
year of 16th birthday.
Youth – U14 From 1st September in the year of
12th birthday to 31st August in the
year of 14th birthday.
Junior From 1st September in the year of
16th birthday to 31st August in the
year of 18th birthday.
Senior From 1st September in the year of
18th birthday.
Under-23 From 1st September in the year of
18th birthday to 31st August in the
year of 22nd birthday.
Veteran From 1st September in the year of
40th birthday.
Vet 40 From 1st September in the year of
40th birthday to 31st August in the
year of 45th birthday.
Vet 45 From 1st September in the year of
45th birthday to 31st August in the
year of 50th birthday.
Vet 50 From 1st September in the year of
50th birthday to 31st August in the
year of 55th birthday.
Vet 55 From 1st September in the year of
55th birthday to 31st August in the
year of 60th birthday.
Vet 60 From 1st September in the year of
60th birthday to 31st August in the
year of 65th birthday.
Vet 65 From 1st September in the year of
65th birthday to 31st August in the
year of 70th birthday.
Vet 70+ From 1st September in the year of
70th birthday.