September is the ninth month on the Gregorian calendar. September is the usual back to school time for most children and the first day of autumn (fall equinox) occurs in this month. Holidays/special days in September are: Labor Day, Grandparents Day. The birthstone is the sapphire and the birth flower is the aster. Retailers will have sales and special offers for back to school items, items associated with the autumn season and much more.