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.
Julius and Augustus didn’t add a month. They replaced a month. The 6th and 7th months had different names, and they simply renamed them to July and August. The actual reason why the month names don’t match up is because Romans originally only counted “business months,” kinda akin to how we count weekdays way more than we count weekends. In any case, no (or little) business was happening in the winter, so they just simply don’t count months during the winter. Those uncounted months would correspond to January and February. When January and February were added, people decided to put them in the front of the calendar rather than at the back. Hence, the 8th month (October) became the 10th month, and so on for all the months.
You can read a bit more from the Wikipedia page here: https://en.m.wikipedia.org/wiki/Roman_calendar#Romulus
Why would they add months at the front? March makes sense to be the first month being spring and all
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