September (i/ˌsɛptˈɛmbər/ sep-TEM-bər) is the ninth month of the year in the Julian and Gregorian Calendars and one of four months with a length of 30 days.September in the Northern Hemisphere is the seasonal equivalent of March in the Southern Hemisphere.In the Northern hemisphere, the beginning of the meteorological autumn is on the 1st of September. In the Southern hemisphere, the beginning of the meteorological spring is on the 1st of September.September begins on the same day of the week as December every year, because there are 91 days separating September and December, which is a multiple of seven (the number of days in the week). No other month ends on the same day of the week as September in any year. This month and May are the only two months to have this property. April and July of the previous year begin on the same day of the week as September of the current year as a common year, October of the previous year always begins on the same day of the week as September of the current year as a leap year, January of the previous year begins on the same day of the week as September of the current year as a leap year and a year immediately before that. In common years, September ends on the same day of the week as April and December of the previous year while in leap years, September ends on the same day of the week as July of the previous year. In years immediately before common years, September begins on the same day of the week as June of the following year and in years immediately before leap years, September begins on the same day of the week as March and November of the following year. In years immediately before common years, September ends on the same day of the week as March and June of the following year and in years immediately before leap years, September ends on the same day of the week as August and November of the following year.September (from Latin septem, "seven") was originally the seventh of ten months on the oldest known Roman calendar, with March (Latin Martius) the first month of the year until perhaps as late as 153 BC. After the calendar reform that added January and February to the beginning of the year, September became the ninth month, but retained its name. It had 29 days until the Julian reform, which added a day.September is mostly in the sixth month of the astrological calendar (and the first part of the seventh), which begins at the end of March/Mars/Aries.September marks the beginning of the ecclesiastical year in the Eastern Orthodox Church.