Answer:
Before Julius Caesar, the calender we use today was not in existence.
Ancient Rome used what was called the 'lunisolar calender' to keep time. This system is based on the cycle of the moon and certain Roman holidays, as a result some years had 11 months and others 13.
Julius Caesar wanted a more consistent calender. for this he turned to a man named Sosigenes, a astronomer from Alexandria, Greece. Sosigenes introduced Caesar to the fact that the earth was a sphere (not flat) with a elliptical orbit around the sun. Sosigenes also introduced Caesar to the important dates of the summer and winter solstice's, and the autumnal and vernal equinox. using these dates as reference points, Julius Caesar introduced the calender we have today, with a 365 days, a leap year every 4 years and 5 alternating months with 31 days instead of 30.
And in honor of this, the month of July bores his name.