The two equinoxes happen in March (marking the start of spring in the Northern Hemisphere) and September (marking the start of autumn). At the moment of the equinox, the Earth's axis is not tilted toward or away from the sun, leading to nearly equal amounts of daylight and darkness.
The science behind equinoxes
The Earth's axis is tilted 23.4° relative to its orbital plane. As the Earth orbits the Sun, this tilt causes different hemispheres to receive more or less direct sunlight at different times of year — creating seasons. At the equinoxes, the Sun is directly over the equator, and the tilt is sideways relative to the Sun, so both hemispheres receive equal illumination. This produces roughly 12 hours of daylight and 12 hours of darkness everywhere.
Equinox dates and precision
The March equinox (Vernal Equinox) occurs around March 20 each year, and the September equinox (Autumnal Equinox) occurs around September 22. The exact time varies by a few hours each year because the Earth's orbit isn't a perfect circle and the calendar year isn't exactly 365.25 days. In 2026, the March equinox is on March 20 at 14:46 UTC, and the September equinox is on September 22 at 18:19 UTC.
Cultural and practical significance
Equinoxes have been celebrated for millennia. The March equinox marks Nowruz (Persian New Year), Holi (in some traditions), and Easter (which is calculated relative to the equinox). The September equinox marks the Mid-Autumn Festival in East Asian cultures. Practically, equinoxes are used by solar panel installers to calibrate tilt angles, by farmers to plan planting schedules, and by navigators to verify compass accuracy.
See our Equinoxes and Solstices 2026 article for exact dates and viewing tips.