September 1 is the first day of the month of September in the Gregorian calendar. It marks the transition from summer to autumn in the Northern Hemisphere, often associated with the start of the school year for many students. This day can also signify the beginning of various seasonal activities and preparations for the upcoming fall. In some countries, September 1 is celebrated as a national holiday. For example, in Russia, it is known as Knowledge Day, when students return to school after the summer break. This day is often filled with ceremonies and festivities to welcome the new academic year.