The days have been getting shorter and shorter in the Chicago area since June, but in the next few days, we’ll hit an important milestone with the earliest sunset of the year.
Astronomers say the day with the least amount of sunlight doesn’t occur until the winter solstice, which occurs on December 21st, but the earliest sunset of the year actually occurs two weeks before that.
This year, that day is December 8th, and the sun sets exactly at 4:21 PM. After that, the sunset slowly begins to slow down, and over the course of eight full days he lengthens by a minute.
Officials say the winter solstice will occur just before 4 p.m. on December 21. The day means “the shortest day” of the year. That means the area will see the least amount of sunshine of the season at just under 9 hours and 11 minutes.
From there, the days will slowly start getting longer, but according to Sunrise-Sunset, we won’t get more than 10 hours of sun again until January 30th.
Even after the summer solstice, sunrise continues to occur late in the morning until January 3, when the sun rises around 7:16 AM. A later sunset offsets that change. Every day, even if the sun rises late.
Naturally, the question arises as to why the earliest sunset and latest sunrise do not fall on the winter solstice. There’s a simple reason for that. Solar time is not the same as clock time and is rarely exactly 24 hours. time.
In fact, “solar noon” rarely occurs at noon local time. When the clocks were changed earlier this week, solar noon moved back from 12:34pm to 11:34am, slowly approaching “clock noon,” according to experts.
“Solar noon” is simply defined as the time when the sun is highest on the horizon, and “solar day” is measured between the “solar noon” time on one day and the next.
Combine that with the Earth’s elliptical orbit and the tilt of the planet’s axis, and you have a time system that is easily out of sync with clocks and calendars. It will be sunrise or sunset.
For those curious, the next real “solar noon” at 12:00 PM in Chicago will be January 16th. Clock noon.