The following year he was murdered on the Ides of March. Unfortunately, Caesar himself was only able to enjoy one July during his life—the very first July, in 45 B. Not only did the Senate name a month after Augustus, but it decided that since Julius's month, July, had 31 days, Augustus's month should equal it: under the Julian calendar, the months alternated evenly between 30 and 31 days with the exception of February , which made August 30 days long. The Julian calendar became the predominant calendar throughout Europe for the next years until Pope Gregory made further reforms in But these changes were ephemeral, and only Julius and Augustus have had two-millenia-worth of staying power.
So to avoid three long months in a row, the lengths of the last four months were switched around, giving us 30 days in September, April, June, and November. So, instead of August having a mere 30 days, it was lengthened to 31, preventing anyone from claiming that Emperor Augustus was saddled with an inferior month. To accommodate this change two other calendrical adjustments were necessary: The extra day needed to inflate the importance of August was taken from February, which originally had 29 days 30 in a leap year , and was now reduced to 28 days 29 in a leap year. The following year he was murdered on the Ides of March.