See our story on the winter solstice from {2019}: https://wapo.st/2JWoZFg via
@justingrieser


Here's the relevant snippet:

Hey
@capitalweather
Can you please remind us #LaymansTermsGang folks why the earliest sunset of the year is over the next few days and NOT on Winter Solstice 12/21? Thanks!
@PoPville

Earliest sunset comes before winter solstice

Posted by Bruce McClure and EarthSky Voices | December 3, 2022



View larger. | The shortest day is at the solstice. But the earliest sunset comes before the solstice, in early to mid-December for latitudes like those in the U.S. Likewise, the latest sunrises come in early January. This map shows the number of days between earliest sunset and latest sunrise, and the dates of the earliest sunsets and latest sunrises themselves, for various latitudes. The dates hold true around the globe. Map via Brian Brettschneider (@Climatologist49 on Twitter, or via Brian B.’s Climate Blog). Used with permission.

Earliest sunset isn’t on the shortest day

For the southernmost U.S. and similar latitudes – around 30 degrees north latitude – the earliest sunsets of the year are happening around now, because they come in late November and early December. For latitudes farther north – around 40 degrees north latitude – the year’s earliest sunsets will happen in the coming week, the week of December 5, 2022. For instance, that would be the latitude of New York City; Philadelphia, Pennsylvania; Kansas City, Missouri; Denver, Colorado; Reno, Nevada; Beijing, China; Madrid, Spain; and Naples, Italy.

Meanwhile, what about the Southern Hemisphere? At this same time, for 40 degrees south latitude, the year’s earliest sunrises happen this week, as you progress toward your longest day at the December solstice.

Then, closer to the Arctic and Antarctic Circles, the earliest sunset and earliest sunrise happen nearer the solstice.

Want to know the date of your earliest sunset (or sunrise)? Sunrise-sunset.org provides the sunrise/sunset times to the second, for locations around the globe.

{snip}

It's almost pitch dark here in Boston, and the sky above the capitol is light. How can that be?

tia
las

The exact date for the earliest sunset or earliest sunrise varies by latitude. Toward the end of the first week of December, mid-temperate latitudes in the Northern Hemisphere have their earliest sunsets. The earliest sunset for 40 degrees N. latitude is on December 7. That would be the latitude of New York City (shown in Jerry Ferguson‘s photo, top of post); Philadelphia, Pennsylvania ; Kansas City, Missouri; Reno, Nevada; Beijing, China; Madrid, Spain; Naples, Italy. Meanwhile, the Southern Hemisphere’s mid-temperate latitudes are waking up to their earliest sunrises.

{snip}

It seems paradoxical. At middle latitudes in the U.S. – and throughout the Northern Hemisphere – the earliest sunsets of the year come about two weeks before the solstice and the shortest day of the year.

Why isn't the earliest sunset on the year’s shortest day? It's because of the discrepancy between the clock and the sun. A clock ticks off exactly 24 hours from one noon to the next. But an actual day - as measured by the spin of the Earth, from what is called one “solar noon” to the next - rarely equals 24 hours exactly.

Solar noon is also called simply midday. It refers to that instant when the sun reaches its highest point for the day. In the month of December, the time period from one solar noon to the next is actually half a minute longer than 24 hours. On December 7, the sun reaches its noontime position at 11:52 a.m. local standard time. Two weeks later - on the winter solstice - the sun will reach its noontime position around 11:59 a.m. That's 7 minutes later than on December 7. ... The later clock time for solar noon also means a later clock time for sunrise and sunset.