This week is a good news, bad news situation.
The bad: the earliest sunsets of the year happen this week in Boston.
The good: in just a few days, sunsets start getting later.
On Tuesday and Wednesday, the sun sets in Boston at 4:11 PM. Sunset times start getting later beginning on Thursday.
Unfortunately, we continue to lose daylight through the Winter Solstice on December 22. On that day, we enjoy just 9 hours and 4 minutes of light. Even after that point, sunrises will continue to get later, too. The earliest sunrises occur during the first week of January.
It’s a common misconception that the latest sunrise and earliest sunset occur on the same day, on the first day of winter.
The difference stems from the way we measure time. On a watch, a day is exactly 24 hours. Scientifically, a day stretches from one solar noon to the next. Solar noon is the time at which the sun reaches its highest point in the sky on any given day.
As you might guess, solar noon is not exactly 24 hours in length. It varies over the course of the year. During the winter, it’s a little bit less than 24 hours.
So, the built up difference between our measured day and the solar day creates an offset between the latest sunrises and earliest sunsets.