The annual winter solstice isn’t until December 21st, but the year’s earliest sunsets are already upon us.
If you step outside any of these first several days of December at 4:32 PM, you’ll watch the Sun make its quickest exit of the year over the western horizon (if there aren’t clouds).
The upshot is that evenings start getting brighter from here.
5 PM sunsets return halfway through January. By late June, our star sticks around every day until 8:40 at night.
Why not on the solstice?
It seems logical that our shortest day on the calendar should have the earliest sunset & the latest sunrise. But it doesn’t happen that way.
The simplest explanation is that a “day” on our clocks doesn’t match perfectly with a “day” in our skies.
The Sun reaches its highest point in our sky every day around noon, but not precisely at 12 PM — it varies by up to 15 minutes either side through the year.
This is because the Earth is tilted on its axis, and its orbit around the Sun is shaped like an ellipse, not a perfect circle.
If you’ve ever noticed sunrise & sunset times don’t change at the same pace through the year, this is why.
Later sunset, but shorter day
Right now, the Sun is taking slightly longer each day to reach its peak in our sky. That will soon cause both sunrise and sunset to shift later and later.
The overall length of day still gets shorter until the 21st because we lose more light in the morning than we gain in the evening.
Later sunrise, but longer day
After the solstice, later sunsets start to out-gain the later sunrises, and our days get longer.
Our latest sunrises of the year, around 7:28 AM, happen the first week of January.