July and August weren't new months added in. They were renamings of the existing months Quintilis and Sextilis. The disconnect between the months' numbers and the names their numbers represent actually comes from a later shifting of the start of the year from March back to January.
10 months used to be the standard, until some Caesers ended up getting a couple of months named after them.
September (7th month) October (8th month) November (9th month) December (10th month)
Those months would also be named appropriately again if we dropped July and August…. But then I’d lose my birthday.
I used to think this too, but it turns out that it's not the case.
July and August weren't new months added in. They were renamings of the existing months Quintilis and Sextilis. The disconnect between the months' numbers and the names their numbers represent actually comes from a later shifting of the start of the year from March back to January.
Well hot damn!