The autumnal equinox in the northern hemisphere will fall on September 22 this year, marking the end of summer. From that moment on, the days become shorter and the nights longer.
As the name suggests, day and night should be equal on this day, but in reality, they are not. The reason is the atmosphere: it refracts the Sun’s rays, causing us to see it a little before it actually rises and a little after it has already set. As a result, we get a few minutes of “extra” daylight.
The actual equinox, when day and night are equal, occurs a few days later, on September 25 or 26, depending on your geographical location.
