The Earliest Sunset of the Year Does Not Fall on the Shortest Day
Clocks fell back on November 1 and evenings turned dark early. But the earliest sunset of the year is still weeks away, and it lands in early December, well before the winter solstice on December 21.
Key points
- Most people assume the darkest evening of the year is December 21, the winter solstice.
- The United States Naval Observatory puts the pattern plainly for 40 degrees north latitude, the line that runs near New York, Philadelphia, Denver and Kansas City.
- The cause is a mismatch between the clock and the sun.
Most people assume the darkest evening of the year is December 21, the winter solstice. It is a reasonable guess, and it is wrong. The solstice is the shortest day of the year, with the least total daylight. But at the latitudes of most United States cities, the earliest sunset arrives about two weeks before it, and the latest sunrise arrives about two weeks after it.
The United States Naval Observatory puts the pattern plainly for 40 degrees north latitude, the line that runs near New York, Philadelphia, Denver and Kansas City. There, the earliest sunset falls around December 8, and the latest sunrise around January 5. Figures published by EarthSky for Philadelphia show how it works. On December 7 the sun rises at 7:09 a.m. and sets at 4:35 p.m., giving 9 hours and 27 minutes of daylight. On December 21 the sun sets later, at 4:38 p.m., yet the day is shorter, 9 hours and 20 minutes, because sunrise has slipped to 7:19 a.m. The morning loses more time than the evening gains.
Two clocks that disagree
The cause is a mismatch between the clock and the sun. Clock days are exactly 24 hours, every day. Solar days, measured from one solar noon to the next, are not. From mid November to early February each solar day runs a few seconds to half a minute longer than 24 hours, the Naval Observatory notes. That small daily excess pushes sunrise, solar noon and sunset a little later by the clock, day after day. In Philadelphia, solar noon moves from 11:52 a.m. on December 7 to 11:59 a.m. on the solstice. Across the season, clock time and sun time can drift apart by as much as 16 minutes. Astronomers call the gap the equation of time.
Two features of Earth's orbit create it. The planet travels on an ellipse, not a circle, and it moves fastest near its closest point to the sun, which falls around January 3. Its axis also tilts about 23.4 degrees. Together those facts stretch and squeeze the length of solar days across the year. In autumn, shrinking daylight pulls sunset earlier each day. By early December that pull weakens, while the clock effect keeps pushing sunset later. The push wins, and sunset starts gaining time even as the days keep getting shorter until December 21. Sunrise keeps losing until early January, when the balance flips the other way.
So the season has three landmarks, not one. First comes the earliest sunset in early December. Then the solstice on December 21, 2026, at 20:50 UTC, brings the shortest day. Then the latest sunrise lands in early January. The November shock has a simpler cause. On November 1, 2026, clocks in the United States moved back one hour, from 2:00 a.m. to 1:00 a.m. The sun kept its schedule. The labels on the day changed. Daylight time returns on March 14, 2027.