IAmSinistar: That actually parallels the Roman calendar, which is no surprise given the overlap of those two cultures. The names of the months are dead giveaways that the Romans numbered them differently, especially since September, October, November, and December begin with the Roman numerical prefixes for 7, 8, 9, and 10. Some of the other month names come from gods (January, June) or Caesars (July, August). Even more tellingly, the old name for August was Sextilis, which includes the prefix for 6.

This system is what is known as the Julian Calendar, after Julius Caesar who oversaw its construction. It began on March and ended on February, which is why we add leap days to February (another Roman invention, and they added the extra days to the end of their year).

The Julian Calendar has been superceded by the Gregorian Calendar in most countries now, but the months retain their previous names, which are now out of alignment with their sequence.

IAmSinistar: No surprise here too, since the term "month" comes from the word "moon". Indeed, it can be read as "moonth", in the same way number suffixes are used - "this is the fourth day", "this is the moonth of ice". A month also roughly approximates one lunar cycle (28 days), though only February hews to it completey (and only then on non-leap years). The rest are padded out to accommodate the solar cycle that forms the year. Many cultures used lunar calendars in preference to solar ones, and some religious observances are still tied to lunar events.