2016 Autumnal Equinox, September Equinox
An Equinox is an astronomical event that happens twice, once in spring and once in autumn, each year when the tilt of the Earth's axis is inclined neither away from nor towards the Sun. During Equinoxes the tilt of the Earth (with respect to the Sun) is 0° and because of it duration of the day and the night are almost equal on Equinox day i.e. 12 hours.
Equinoxes occur on 20th or 21st March and 22nd or 23rd September each year and both days has equal length of the day and the night.