AUSTIN (KXAN) — While we haven’t reached the winter solstice yet (Dec. 21) we’re already experiencing the earliest sunsets of the year in Central Texas (and really most of the Northern Hemisphere).
5:30 p.m. is the earliest the sun sets each year in Austin. Nov. 25 was the first Austin sunset of the year at 5:30 p.m. and it will continue to set at 5:30 p.m. through Dec. 10.
On Dec. 11 the sun sets in Austin at 5:31 p.m. and will continue getting later until late June/early July when we reach the latest sunset of the year at 8:36 p.m.
Unfortunately, while our sunsets will soon start to get later, our sunrises will continue getting later as well. We don’t experience our latest sunrises of winter until Jan. 4-15 when the sun doesn’t rise until 7:28 a.m.
This, however, is not our latest sunrise of the whole year, but just our latest sunrise of standard time. Our latest sunrise of the whole year happens the day before we end Daylight Saving Time. On Nov. 5 the sun rises at 7:48 a.m., the latest sunrise we ever see.
Why doesn’t the latest sunset occur on the winter solstice?
Several complicated factors mean that the earliest sunset of Standard Time happens before the winter solstice, but the latest sunrise happens after the winter solstice.
Basically, it comes down to errors made by assuming a day is 24 hours long all year round.
A day is really the time it takes to go from one solar noon to the next one. Solar noon is when the sun reaches its highest point in the sky, which rarely happens at exactly 12 p.m.
The elliptical orbit around the sun, the tilt of the earth’s axis and the position of the sun within our orbit all help to shift the length of our days away from being an even 24 hours. In reality, sometimes a solar day is longer than 24 hours and sometimes it’s shorter.
All these adjustments and rounding errors, along with the latitude you’re located at, mean that our sunsets stop getting earlier before our sunrises stop getting later, but the shortest day of the year is still on the winter solstice.