The actual time will depend upon your timezone, but the Sun will be directly overhead at midday on September 22nd, 2014, at 2:29 UTC (Universal Time) at the equator. That would be at 10.29pm EDT, the author’s timezone. This marks the start of Autumn in the Northern Hemisphere and Spring in the Southern Hemisphere.
Traditionally and technically, this means the days are of equal time as the night. But this doesn’t last long, and by mid October the days will start becoming noticeably shorter and shorter and the nights much longer. Folks here in my neck of the woods call this “going into the tunnel”.
This date is called an equinox from the Latin term “equal night”. Actually, the term relates to the Earth’s orbit position and tilt relative to the Sun. In Winter, the Earth’s northern pole is tilted away from the Sun, and conversely the southern pole is tilted towards the Sun. In Summer, the opposite is the case. The Spring and Autumn Equinox occur when the Earth’s wobble is exactly static, and the Sun is directly over the equator at mid day.
So when you wake up the morning of September 23rd, it will be Fall. Or if you’re a night owl like myself, you can experience Fall at 10:29pm EST on the 22nd.