I was looking over some sun tables recently when it suddenly struck me that the time difference, over the course of a year, between earliest sunrise and latest sunrise is much smaller than the time difference between earliest sunset and latest sunset.
But for the life of me I could not figure out why. And then the light bulb came on!
Here are the numbers, all for Caribou:
Earliest Sunrise: 4:37 a.m. Latest Sunrise: 7:17 a.m. Difference: 2 hours, 50 minutes.
Earliest Sunset: 3:43 p.m. Latest Sunset 8:31 p.m. Difference: 4 hours, 48 minutes.
If you’d like, have fun with the family and see if anyone can reason it out, before reading the answer below!
Here’s the answer. That big difference has only to do with a single fact. We move our clocks ahead by one hour in March, and back by one hour in November. But when factoring that out, in other words, if we never changed the time, the difference vanishes. And here’s the proof.
Earliest Sunrise becomes 3:37 a.m., now that we are not “springing forward” by one hour. Latest sunrise remains in “Standard Time”, so it stays at 7:17 a.m. The difference, which was 2 hours, 50 minutes, is now 3 hours, 50 minutes.
Earliest Sunset remains in “Standard Time”, so is still 3:43 p.m., but latest Sunset becomes 7:31 p.m., not 8:31 p.m., because by then we would have already moved ahead by one hour, but remember, we are not moving the clocks at all in order to solve this “mystery”. So the difference, which was 4 hours, 48 minutes, becomes 3 hours, 48 minutes.
So now we can see that without moving the clocks at all, the maximum differences in time between earliest and latest sunrise and earliest and latest sunset is basically the same.
It is merely our “time intervention” which has led to the evening difference (earliest to latest sunset) being about two hours longer than the morning difference (earliest to latest sunrise).
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at tshapiro@wagmtv.com.
