Year’s fastest sunsets happen around equinoxes

Fastest sunsets: A sailboat in front of the enormous sun, which is topped with green smudges. Thin orange clouds above. — View at EarthSky Community Photos. | Jim Grant caught this sunset with a green flash at the Ocean Beach Pier in San Diego, California, on July 19, 2023. Jim wrote: “I knew the sunset was going to be stunning and I started tracking the boat hoping to get it centered in the sun. The green rim and green flash above were a bonus.” Thank you, Jim! Read more about the fastest sunsets below.

Year’s fastest sunsets and sunrises

The September equinox will arrive Saturday (September 23, 2023) at 6:50 UTC. And here’s a little-known equinox phenomenon: the sun sets faster around the time of an equinox. The fastest sunsets (and sunrises) occur at or near the equinoxes. On the other hand, the slowest sunsets (and sunrises) occur at or near the solstices. It’s true whether you live in the Northern or Southern Hemisphere.

And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.

Why does the sun set so quickly around the equinoxes? It’s because, at every equinox, the sun rises due east and sets due west. So, that means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.

Bright sun with rays just on the horizon, under light clouds, seen across rolling hills. — View at EarthSky Community Photos. | Ragini Chaturvedi, a frequent contributor to our pages, caught this sunrise from Palouse, Washington, on June 22, 2021, the day after the solstice. She wrote: “Encouraged by the EarthSky community, I share another phenomenal view of Palouse, Washington. At the elevation of 3,612 feet [1,100 m], the Steptoe Butte State Park presents such a super early sunrise view. Breathtaking.” Thank you, Ragini!

Year’s slowest sunsets and sunrises

Meanwhile, at a solstice, the sun is setting farthest north or farthest south of due west. And, the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. So that means a longer duration for sunset at the solstices.

Also, the sunset duration varies by latitude. Farther north or south on the Earth’s globe, the duration of sunset lasts longer. Closer to the equator, the duration is shorter. But let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States; parts of Spain; and Beijing, China.

At that latitude, on the day of equinox, the sun sets in about 2 3/4 minutes.

On the other hand, the solstice sun sets in roughly 3 1/4 minutes at 40 degrees latitude.