The equinox

On the day of the equinox, also known as the equinox, the sun is exactly over the equator. This happens twice a year, once in spring and once in fall. The equinox in spring is also known as the vernal equinox, while the one in fall is known as the autumnal equinox. The vernal equinox this year occurred on March 20, 2024 at 4:06 am.

On the day of the equinox, the duration of day and night are theoretically the same. This is because the sun is perpendicular to the equator and the day and night hours are approximately the same length. However, the day actually appears longer than the night for two main reasons:

• Solar disk: The solar disk is perceived as a visible disk that rises and sets above the horizon. The time between the first visible appearance of the solar disk on the horizon and its final disappearance after sunset, in each case in relation to the upper edge, is regarded as "day", which leads to an apparent lengthening of the day. The equinox, on the other hand, refers to the center of the solar disk.
  
  
• Atmospheric refraction: Sunlight is refracted by the Earth's atmosphere, causing it to deflect slightly and making the sun appear to be above the horizon, even though it has actually already set. This leads to an extended period of daylight.

Due to these two factors, the day actually appears longer than the night during the equinox, although the duration of day and night should theoretically be the same.