"Vernal Equinox" It falls on 20 March 2026, the moment when the sun is exactly perpendicular to the Earth's equator, causing day and night to be equally long.
FacebookNARIT, the National Astronomical Research Institute of ThailandPosted that "20 March 2026 is 'Vernal Equinox,' when daytime equals nighttime." The sun will rise exactly from the eastern horizon and set exactly in the west. This marks the day when countries in the Northern Hemisphere enter spring, and countries in the Southern Hemisphere enter autumn. 'Vernal Equinox' (pronounced wa-san-ta-wi-su-wat) derives from the Sanskrit word 'Equinox,' meaning 'equal night point,' referring to the sun's position perpendicular to the Earth's equator, resulting in equal day and night durations.
In Thailand, on this day, the sun will rise at approximately 06:22 and set at about 18:28 (Bangkok time). This marks the transition of the Northern Hemisphere into spring and the Southern Hemisphere into autumn.
The definition of sunrise and sunset times for this phenomenon counts the moment the sun's upper edge touches the horizon. That is, sunrise is recorded when the sun's upper edge touches the eastern horizon, and sunset when the upper edge touches the western horizon (or when the sun fully disappears below the horizon). This can make sunrise and sunset times appear unequal, but it does not mean day and night lengths differ. Counting from when the sun's center crosses the horizon, this day has exactly 12 hours of day and 12 hours of night.
Seasons on Earth occur because the Earth's axis tilts 23.5 degrees relative to the plane of its orbit around the sun. This causes varying sunlight angles and heat energy received worldwide, resulting in temperature differences and varying day and night lengths. This is why Earth experiences seasons.
You can observe that in summer, daytime is longer than nighttime, with the sun rising earlier and setting later. Conversely, in winter, nighttime is longer than daytime, with the sun rising later and setting earlier.
The next related solar event is the 'Summer Solstice' on 21 June 2026, when the sun rises at its northernmost point northeast and sets at its northernmost point northwest. This day has the longest daytime of the year, marking the Northern Hemisphere's entry into summer and the Southern Hemisphere's entry into winter.
Thanks to Facebook NARIT, the National Astronomical Research Institute of Thailand