In the original 10 month Roman calendar, August was the sixth month with 30 days and was originally named Sextilis. In 8 BC, the Roman Senate rewarded Octavian Augustus a month in his honor. The founder and first emperor of the Roman Empire, Octavian Augustus selected Sextilis, which under the Julian calendar was the eighth month with the addition of January and February.
Renamed to Augustus, there remained the issue of the month having fewer days than Julius (July). Whether Octavian adjusted the number of days to match that of July is uncertain, but the result left February with 28 days except in a leap year and September and November each gave up a day to October and December to avoid a trifecta of 31 days in a row. For hubris or pride or both, the Julian calendar came to be.
View more at http://www.nationaldaycalendar.com/august-overview/