If you mean Caesar and Augustus, they are actually the reason we don't have even more badly named months, like Quintilis (July) and Sextilis (August). December

If you mean Caesar and Augustus, they are actually the reason we don't have even more badly named months, like Quintilis (July) and Sextilis (August). December was the tenth month simply because each new year started in March. This likely changed long before Caesar was even born. They also, allegedly, had only ten months, but the second king of Rome changed that, but it could also be just a legend.