September 22, 2017 all-day
In the Northern Hemisphere, autumn begins today with the autumnal equinox, at 10:21 AM, EDt. Note that in the Southern Hemisphere todayis the beginning of spring. Everywhere on Earth (except near the poles) the sun rises due east and sets due west and daylight length is nearly identical about 12 hours, 8 minutes. Read more at http://earthsky.org/astronomy-essentials/everything-you-need-to-know-september-equinox.
Image courtesy of NASA.