It’s nearly springtime – according to the official calendar, that is.

Tuesday will bring the arrival of the vernal equinox, which signals the beginning of the spring season in the Northern Hemisphere.

What is the definition of this? Here are the details regarding how we divide the year based on the Earth’s orbit.

The Earth orbits the sun at an inclined angle.

During the majority of the year, the Earth’s axis is angled towards or away from the sun, resulting in unequal distribution of the sun’s heat and light on the northern and southern hemispheres of the globe.

During the equinox, the Earth’s tilt and its path around the sun align to provide equal amounts of sunlight to both the northern and southern hemispheres.

The term equinox is derived from the combination of two Latin terms that mean “equal” and “night”. This is because during the equinox, the duration of daylight and darkness is nearly the same, although there may be a slight variation depending on one’s location on Earth.

The vernal equinox, which marks the arrival of spring in the Northern Hemisphere, can fall on any date ranging from March 19 to March 21, depending on the year. Similarly, the autumnal equinox, which signifies the beginning of fall, can land between September 21 and 24.

The solstices signify the moments in a year when the Earth is tilted furthest toward or away from the sun. This results in significant variations in the amount of sunlight received by the two hemispheres, causing highly unequal durations of daytime and nighttime.

During the summer solstice in the Northern Hemisphere, the top half of the Earth leans towards the sun, resulting in the longest day and shortest night of the year. The date of this event typically falls between June 20th and June 22nd.

During the winter solstice, which occurs between December 20 and 23, the Northern Hemisphere is tilted away from the sun. This results in the shortest amount of daylight and the longest period of darkness in the year.

These are simply two distinct methods to divide the year.

The weather determines the meteorological seasons, dividing the year into three-month periods according to the temperature patterns. According to this system, spring begins on March 1, summer on June 1, fall on Sept. 1, and winter on Dec. 1.

The Earth’s movement around the sun is what determines the astronomical seasons.

The beginning of spring and autumn is signified by equinoxes, while solstices mark the start of summer and winter.

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The Howard Hughes Medical Institute’s Science and Educational Media Group provides support to the Associated Press Health and Science Department. The AP is solely responsible for all of its content.