I know this is a joke/meme, but I sincerely think of the Roman Empire a surprising amount of times. I find myself obsessing over how Roman citizens were living just as complex lives as we are today, or about Marcus Aurelius’ life and philosophy, or about how the Republic fell and became a totalitarian state.
If I recall correctly, it was mainly political. I’m not an expert in this topic at all, I’m just regurgitating what I read. But from what I remember, it was something along the lines of elections occur at the end of the year, and by placing January and February at the beginning rather than at the end, the new year would more closely coincide with office terms