2 days a year day and night are equal lengths, everywhere on earth. Those days are called equinoxes, by the way today is one of them. Thank you NASA for the info.

Earth is tilted as you may know. Those two days, the North and South poles run straight from north to south. Thus the sun shines exactly over the equator.  Something also cool coming up later on this year, a total solar eclipse on Aug. 21, 2017.