It was the Romans who inserted a leap month inside February between the 23rd and 24th. Since the two consuls ruled on alternating months, adding an extra month after February would give one consul one more ruling month, making it somewhat unfair. Since leap years were handled irregularly back then, they were leap months, not leap days.
The Julian calendar introduced the leap day instead, and maintained it in February as originally, and introduced it every 4 years (except years dividable by 100).
This is also around the same time that July and August were named to their current names (named after Caesar and Augustus). Before that, they had had names equal to fifth and sixth month, respectively, like September comes from seventh.
I recently read that the reason February has only 28 or 29 days, and not 29 or 39, as you'd expect, is because Augustus wanted his month to have just as many days as Julius' month.
No idea if that's true, but sounds appropriate for the ego of an emperor.
Are you suggesting that the men were known as Julius Caesar and Augustus Caesar? Because that's wrong[0]. Augustus used this name and it became a title for roman Emperors, in reference to Julius Caesar. If people are talking about Caesar, they mean Julius Caesar.
I understand that people often refer to Julius Caesar as "Caesar", but to me at least, it mainly refers to the "title" (though that remains a surname, as succession was hereditary, mostly through adoption).
History is not my field, I am probably making multiple mistakes and oversimplifying, but I don't see something in that link that disproves what I said. Today, we often refer to Augustus as Augustus Caesar or Caesar Augustus (less frequently, Emperor Augustus). I also think it's interesting to point out Julius's first name in light of the previous discussion, as that's where the month name comes from.
If we're splitting hair, Octavian was adopted into the gens Julia, so he was a Julius as much as he was a Caesar, and his full name before ascending to emperor was Gaius Julius Caesar Octavianus.
The Julian calendar introduced the leap day instead, and maintained it in February as originally, and introduced it every 4 years (except years dividable by 100).
This is also around the same time that July and August were named to their current names (named after Caesar and Augustus). Before that, they had had names equal to fifth and sixth month, respectively, like September comes from seventh.