March 20 marks Vernal Equinox with equal day and night

March 20, 2026 will mark the Vernal Equinox, the day when daytime and nighttime are nearly equal in length, according to the National Astronomical Research Institute of Thailand (NARIT).

On this day, the Sun is positioned directly above the Earth’s equator, causing day and night to last almost exactly the same duration. The Sun will rise precisely in the east and set precisely in the west.

The Vernal Equinox marks the moment when the Northern Hemisphere enters spring, while the Southern Hemisphere moves into autumn.

The term “Equinox” comes from the Sanskrit-derived word meaning “equal night”, referring to the point when the Sun lies directly above the Earth’s equator, resulting in nearly equal hours of daylight and darkness.

For Thailand, the Sun will rise at approximately 06:22 and set at around 18:28 Bangkok time on that day.

The apparent difference between sunrise and sunset times occurs because sunrise and sunset are defined by the moment the upper edge of the Sun touches the horizon. When the centre of the Sun crossing the horizon is used as the reference point, day and night are each exactly 12 hours long.

Seasons on Earth occur because the planet’s axis is tilted by about 23.5 degrees relative to its orbital plane around the Sun. As Earth revolves around the Sun, different regions receive varying angles and intensities of sunlight, producing differences in temperature as well as the length of day and night.

During summer, daytime becomes longer and the Sun rises earlier and sets later, while in winter the opposite occurs, with longer nights and shorter days.

The next key solar event related to the Sun’s rising and setting positions will be the Summer Solstice on June 21, 2026, when the Sun rises and sets at its most northerly points on the horizon. This produces the longest day of the year in the Northern Hemisphere, marking the start of summer there and the beginning of winter in the Southern Hemisphere.