The spring equinox in the year 2025

The spring equinox in the year 2025 will occur on March 20 at 11:01:30.18 AM, Romanian Legal Time.

The Earth follows an orbit in space, which can be approximated as a great circle. The plane in which Earth's orbit lies is called the ecliptic plane. From Earth's perspective, it is equivalent to consider that the Sun follows the same orbit around a fixed Earth.

On the other hand, the Earth is tilted in space, so its rotational axis is not perpendicular to the plane of its orbit, meaning it is not perpendicular to the ecliptic plane. However, by definition, its rotational axis is perpendicular to the plane defined by the equator. This plane is called the celestial equatorial plane. The two planes—the ecliptic plane and the celestial equatorial plane—are therefore inclined relative to each other.

Thus, by definition, the moment of the equinox is the instant when the Sun is located at the specific point determined by the intersection of these two fundamental planes. In other words, during the equinoxes, the Sun is in the plane of the celestial equator. Since there is only one celestial equator (which divides the Earth in two and is perpendicular to its axis of rotation) and only one Sun, the moments of the equinoxes are unique, regardless of our location on Earth.

We define the dates of the equinoxes and solstices, which mark the beginning of the astronomical seasons, as the moments when the apparent planetocentric longitude of the Sun (including the effects of aberration and pole motion) is an exact multiple of 90°.

In the year 2025, the spring equinox will occur on March 20 at 9:01:30.18 AM Coordinated Universal Time (UTC). For Romania, this moment corresponds to March 20, 2025, at 11:01:30.18 AM Romanian Legal Time. The spring equinox for countries in the Northern Hemisphere corresponds to the autumn equinox in the Southern Hemisphere.

Published on: Mar 18, 2025