A Works Progress Administration Poster, from 1940
, for September
In the old Roman calendar, September was the seventh month, which is where it got its name ("Septem" means "seventh"). The ninth month at the time was November ("Novem" means "ninth"). With Julius Caesar's calendar reform, September became the ninth month, with 30 days. September comes after August and before October.
September begins on the same day of week as December every year, as each other's first days are 13 weeks (91 days) apart. No other month in any year, common or leap year, ends on the same day of the week as September.
In common years, September starts on the same day of the week as April and July of the previous year, and in leap years, October of the previous year. In common years, September finishes on the same day of the week as April and December of the previous year, and in leap years, July of the previous year. In leap years and years immediately after that, September starts on the same day of the week as January of the previous year.
In years immediately before common years, September starts on the same day of the week as June of the following year, and in years immediately before leap years, March and November of the following year. In years immediately before common years, September finishes on the same day of the week as March and June of the following year, and in years immediately before leap years, August and November of the following year.
September is one of two months to have an equinox (the other is March, its seasonal equivalent in both hemispheres), where both day and night are roughly of equal length, occurring either on the 22nd or 23rd, half way between the June and December solstices. In the Northern Hemisphere, Autumn (Fall) begins in this month, while in the Southern Hemisphere, this is the beginning of Spring. For meteorologists, the people who study the weather, these seasons begin on September 1 in those hemispheres. In most Northern Hemisphere countries, school starts in this month, following the summer holidays.
In Ancient Greece, September was called Boedromion. The Anglo-Saxons called it Gerstmonath, meaning "Barley month", referring to the harvest. In other countries, it is referred to as Autumn Month, such as in Finland (Syyskuu) and German-speaking parts of Switzerland (Herbstmonat).
Ethiopian New Year occurs in September. Jewish New Year also often occurs in this month.