This meme shows up every year at this time and while it's funny it's not quite true, and an excellent opportunity to learn more about the Roman calendar!
Yes, Julius Caesar did reform the calendar and yes the motnhs July and Augustus were renamed after him and Augustus. But there had been 12 months for a lot longer!
The reason two months were added in goes back to very early Roman times, when they counted winter as one long month rather than three. When they decided to divide it up, it led to two extra motnhs coming in. This is the simplified version of course!