In the original Roman calendar, the month of August was originally named Sextilis in Latin, because it was the sixth month in the original ten-month Roman calendar under Romulus in 753 BC, when March was the first month of the year. About 700 BC it became the eighth month when January and February were added to the year before March by King Numa Pompilius, who also gave it 29 days.
When Julius Caesar created the Julian calendar in 45 BC, two days were added giving the month 31 days. In 8 BC the month was later renamed Augustus in honour of the first emperor of Rome, Caesar Augustus. (despite common belief, he did not take a day from February. In the Southern Hemisphere, August is the seasonal equivalent of February in the Northern Hemisphere.