What Number of Month is September
September month number is 9 and it is the ninth month of the year.
September is the ninth month of the year and takes its name from the Latin word "septem," which means "seven." This seems strange, as September is the ninth month, but it makes sense when we consider that it was originally the seventh month in the Roman calendar, which began in March.
When did September stop being the 7th month?
During the reign of King Numa Pompilius (circa 713 BC), the Roman calendar underwent some revisions which included the addition of two new months, namely January and February. In 153 BCE, January 1 was officially recognized as the first day of the year, causing September to be designated as the ninth month.
September had originally 29 days, but in the year 46 BCE with the Julian Calendar reform September was expanded to 30 days. September marks the end of summer and the beginning of autumn, which takes place at the autumnal equinox, around September 22 or 23.