September (Roman month) was adjusted to September 1 in the 5th century to coincide with the tax year. September (Roman month) September (from Latin "septem", "seven") or mensis September was originally the seventh of ten months on the ancient Roman calendar that began with March ("mensis Martius", "Mars' month"). It had 29 days. After the reforms that resulted in a 12-month year, September became the ninth month, but retained its name. September followed what was originally Sextilis, the "sixth" month, renamed "Augustus" in honor of the first Roman emperor, and preceded October, the "eighth" month that like September retained its numerical name contrary
Lithuanian calendar month names on this artifact are expressed in symbols, based on natural phenomena and agricultural cycles. (i.e. the sidereal month was divided into three parts). The Julian calendar was used in the Grand Duchy of Lithuania; the Gregorian calendar was adopted by the Polish-Lithuanian Commonwealth in 1586, a few years after its promulgation in 1582 by Pope Gregory XIII. In 1800, following Lithuania's annexation by the Russian Empire, the Julian calendar again became the norm, although a part of ethnic Lithuania left of Nemunas River (Suvalkija) retained the Gregorian calendar (see Aleksotas). The Russian Revolution of 1917 re-instated the Gregorian