I always wondered why the Romans would invalidate the names of the months September and through December. Why didn't they rename these months to reflect their new numerical position?
I even know that the original names for these months were qunitilis and sextilis, which begs the question, "Why aren't these names consistent with their position either?"
August and July didn't throw off the rest of the months of the year. In the original Roman calendar, the year began in March. It was the season for going off to war (Mars is the god of war and march is literally, well marching). Their lunar calendar was 10 months long and January and February were basically really long leap year days.
That is, a lunar calendar would eventually get off cycle (because there aren't exactly 12 lunar cycles in a year). So everything after the end of December and before the spring equinox (which was the start of March) was just 'winter' and winters would have varying lengths. So July was the fifth month of the year, and August was the 6th month of the year. It was only later on that months were tacked onto the beginning of the year
hi, you may be interested in this section of the FAQ, particularly the first, second and fourth posts