The upcoming vernal equinox is set to take place on March 20. 2025, marking the transition into spring in the Northern Hemisphere while the Southern Hemisphere moves into autumn. This astronomical event occurs twice a year when day and night are nearly equal in length across the globe. The phenomenon is attributed to Earth’s axial tilt of approximately 23.5 degrees, which determines how sunlight is distributed throughout the year. The equinox signifies a point where the planet is neither tilted towards nor away from the Sun, resulting in almost equal hours of daylight and darkness.

What Causes the Equinox?

According to research, the equinox occurs due to Earth’s orbital movement around the Sun while maintaining a fixed axial tilt. The alignment ensures that the Sun is positioned directly above the equator. This leads to an even distribution of sunlight across both hemispheres, creating a balance between daytime and nighttime hours. However, complete equality is not achieved as atmospheric refraction and the Sun’s apparent size cause a slight variation in the actual duration of daylight. Reports indicate that locations at the equator receive approximately 12 hours and 6 minutes of daylight, while regions at higher latitudes may experience slightly longer daylight hours.

Equinox Dates and Variations

Sources confirm that equinoxes do not always fall on the exact same date each year. While typically occurring around March 20 and September 22, slight variations arise due to the additional fraction of a day in Earth’s annual orbit. The timing of the equinox shifts gradually as the extra quarter-day accumulates, influencing the calendar date. Meteorologically, spring is considered to begin on March 1, while the astronomical definition aligns with the equinox.

Cultural Significance and Historical Observations

Ancient civilisations have long tracked equinoxes, incorporating them into agricultural cycles and cultural practices. Historical records highlight that structures such as Angkor Wat in Cambodia and El Castillo in Mexico were designed to align with the equinoxes, demonstrating their significance in early astronomy. The phenomenon continues to hold importance in various traditions, with some cultures observing it as a time of reflection and seasonal transition.