“Equinox” comes from the Latin words “equi” meaning “equal” and “nox” meaning “night.” This implies equal amounts of daylight and darkness, however this is not exactly the case. On September 23, 2015, the sun will rise at 6:56 a.m. EDT on the equinox and will set at 7:04 p.m., so there will be 8 minutes of day over night. Although the sun is perfectly over the equator, we mark sunrises and sunsets at the first and last minute the tip of the disk appears. And because of atmosphere refraction, light is bent which makes it appear as though the sun is rising or setting earlier.
By the way, this year, equal day and night won’t occur until September 26 with sunrise as 6:59 a.m. EDT and sunset at 6:59 p.m.