Earlier quoted context omitted.
And in that calender, February is the last month, which makes it the logical month for adjusting leap years.
It looks like there's a legend that this was the case, but January has been the first month of the year through all of recorded history, and Julius Caesar's version was no different. EDIT: Because there's a lot of confusion in several replies I thought I'd clarify: February was the second month in Julius Caesar's calendar. Romans in the Republic describe the month as being at some point the last month in the calendar…
Are you kidding? Not only are September through December literally named "Month 7" through "Month 10", but the year began in late March as recently as AD 1751. That is not a period where we're suffering from a lack of recorded history.