Today is the autumn equinox... meteorologically the first day of Autumn (Fall).
"Autumn according to the meteorological calendar begins in September and ends in November. In the astronomical calendar, the beginning of autumn is marked by the autumn equinox which occurs around the 22 September.
During the autumn equinox, the Sun shines directly on the equator and day and night around the globe are of almost equal length - a day and night of roughly 12 hours each."