How many hours of daylight does the equator experience on September equinox?

On the September equinox, which typically occurs around September 22nd or 23rd, the Earth's axis is tilted neither toward nor away from the sun [c1, t3]. During this event, the sun's direct rays fall vertically on the equator at noon [c1, c3]. Theoretically, this results in 'equal nights' (equinox), where all parts of the world experience approximately 12 hours of daylight and 12 hours of darkness [c1, c2, t10]. While atmospheric refraction and the sun's disk size can slightly extend daylight by a few minutes (making it roughly 12 hours and 6 minutes at the equator), the standard astronomical and geographical definition for the length of day at the equator during an equinox is 12 hours [c2, t2, t5]. This balance occurs because the geometric center of the sun is above the horizon for exactly half the day [t10].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 19: The Motions of The Earth and Their Effects > Equinox > p. 254
2. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > FASCINATING FACTS > p. 179
3. [3] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > THE ALTITUDE OF THE MIDDAY SUN > p. 7
4. [4] https://www.weather.gov/dvn/Climate_Astronomical_Seasons
5. [5] https://www.bbc.com/weather/articles/cwynx6xy3gyo