Autumnal Equinox Marks Shift in Earth’s Seasons

Fall weather is soon expected to grace the Northeast just as the official start of the season, the autumnal equinox, arrives. The autumnal equinox, which can land on either September 22 or 23 depending on the year, marks a pivotal moment for the Earth’s rotation and seasonal changes. According to experts, this year the equinox will occur on Sunday, September 22, at precisely 8:44 a.m. Eastern time in the Northern Hemisphere.

The phenomenon of the equinox occurs due to the Earth’s tilted rotation around the sun. Throughout most of the year, the sun’s warmth and light affect the northern and southern hemispheres unequally. However, during equinoxes, the sun shines directly above the Equator, resulting in nearly equal day and night times globally.

As explained by the Old Farmer's Almanac, “On every other day of the year, either the Northern or Southern Hemisphere is inclined toward the sun because the Earth’s axis is tilted 23.4 degrees,” implying that one hemisphere receives more sunlight than the other. With the equinox marking the beginning of fall, the Northern Hemisphere will see days shortening as nights lengthen leading up to the winter solstice on December 21.

This natural occurrence signifies an intersection between solstices. The summer solstice occurs when the Northern Hemisphere is tilted toward the sun, marking summer’s start. Conversely, the winter solstice takes place when the Southern Hemisphere receives more sunlight, denoting winter in the North.

Alongside the equinox and solstice changes, daylight saving time is also a consideration for the United States. Under the 2005 Energy Policy Act, daylight saving begins the second Sunday in March and concludes the first Sunday of November. This year, clocks are set to roll back one hour on Sunday, November 3, at 2 a.m.

Daylight saving time was adopted in the U.S. in 1918 but faced periods of abolishment before becoming standard under the Uniform Time Act of 1966. Although most U.S. states partake in this practice, exceptions include Arizona, Hawaii, and several U.S. territories.