Sorry to contradict,
Caprice!
The calendar was changed by
Julius Caesar and again by his descendant
Augustus. Previously it had been:
1. January
2. February
3. March
4.
April5.
May6.
June7.
September8. October
9. November
10. December
Julius and then
Augustus decided that there should be more months, named after themselves, giving us
July and
August, and pushing
September onwards two steps away from numerical logic!
:-)