Today's sunset was earliest of the year, but why not on Winter Solstice?
Winter solstice is the shortest day of the year in terms of daylight, but contrary to popular belief, it does not have the latest sunrise or the earliest sunset of the year.
Timeanddate.com breaks down the confusion, explaining the discrepancy is between our modern-day timekeeping methods and how time is measured using the sun. This is known as the equation of time.
The earliest sunset actually occurs a few days before the solstice and the latest sunrise happens a few days after.
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For New York City, the winter solstice date for 2020 lands on December 21 at 5:02 a.m.
However, the earliest sunset date occurs on December 7 at 4:28 p.m., while the latest sunrise date arrives on January 3 and 4, 2021 at 7:20 a.m.
The equation of time is calculated as 'apparent solar time - mean solar time.'
That is the difference between time measured using a sundial, and time measured using a clock.
Most clocks run on the idea that a day is exactly 24 hours. However, a day is technically the duration between one solar noon, the time of the day when the sun is the highest point in the sky, to the next.
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The length of a solar day is not exactly 24 hours long. It varies throughout the year because of the elliptical shape of Earth's orbit and the tilt on its axis.
It's longer than 24 hours around the summer and winter solstices and shorter than 24 hours around the spring and fall equinoxes.
However, dates for the earliest sunset and latest sunrise also depend on a location's latitude.
Locations closer to the equator have their earliest sunset sometime in November.
Locations at higher latitudes have their earliest sunset later, closer to the actual date of the winter solstice.
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