People in Seattle say the evenings vanish in September. People in Miami barely notice. Both are right, and the reason is a single angle.
The numbers
| Place | Latitude | Sunset change per day, Sept 20 | Per day, June 21 | Daylight, June 21 | Daylight, Dec 21 |
|---|---|---|---|---|---|
| Quito, Ecuador | 0°S | −0.3 min | +0.2 min | 12 h 07 | 12 h 08 |
| Miami, FL | 26°N | −1.1 min | +0.2 min | 13 h 45 | 10 h 32 |
| Houston, TX | 30°N | −1.3 min | +0.2 min | 14 h 04 | 10 h 14 |
| Detroit, MI | 42°N | −1.8 min | +0.2 min | 15 h 17 | 9 h 05 |
| Seattle, WA | 48°N | −2.0 min | +0.2 min | 15 h 59 | 8 h 26 |
| Anchorage, AK | 61°N | −3.2 min | +0.0 min | 19 h 23 | 5 h 27 |
2026. Negative means sunset is getting earlier. Computed with the same NOAA solar geometry the checker uses, at each place's own civil time.
Why latitude decides it
Day length depends on how far the sun's path is tilted against your horizon, and that tilt is your latitude. On the equator the sun's path stands vertical, so the seasonal change in the sun's declination barely changes how long it stays up: sunset moves less than a minute a day all year. At 47° the path leans over, and the same change in declination stretches or shrinks the day much more. Near the poles the effect runs away, which is why Anchorage gains and loses hours where Miami gains and loses minutes.
The rate is fastest at the equinoxes, when the declination is changing quickest, and drops to zero for a few days at each solstice. September and March are where the drift is felt, and they are also the months the sun rises due east: the two effects land together, which is why the glare season arrives so abruptly in the north.
What it means for a drive
In Detroit, sunset moves about 1.7 minutes earlier each day in September. A westbound drive home that was fine at 6:30 in August is in the sun by mid-month and clear again in November when the sun sets before you leave. Every city page lists today's drift and the date each departure clears: sun glare by city.