A clock face

This morning, people across the country woke up a little tired, robbed of an hour of sleep. Our collective semiannual cycle through the stages of Daylight Saving Grief is somewhere between anger and bargaining. After the inevitable proposals that we abolish the practice entirely, we’ll slowly reach acceptance. Until November, that is.

Who knows? Maybe this really will be the last daylight savings change for many of us. West Coast states and others have asked the federal government to allow them to stay on daylight time—with more light in the evening—the entire year.

The time zone shift is a good opportunity to study what daylight in the U.S. looks like now, and what would it look like if we stayed on Daylight Saving Time the whole year.

Sun Stripes

These maps show the earliest and latest sunsets (across the year) around the country under the current system. West Texas has the latest sunset in December, while western North Dakota and the west part of Michigan’s Upper Peninsula has the latest sunset in June. (Alaska and Hawaii aren’t shown, as their sunset and sunrise times can be very different from those in the lower forty-eight. There’s also some strange artifacts in the Arizona data.)

The picture is broadly similar for sunrises. The latest December sunrises are in western North Dakota and the western part of the Upper Peninsula; the earliest June sunrises are in West Texas.

Notice that for both sunrise and sunset times, the stripes run in different directions for December and June. On the June solstice, Bismarck, North Dakota and Mobile, Alabama both have their earliest sunrise at 5:45 a.m., but the sun sets at 8 p.m. in Mobile and 9:45 p.m. in Bismarck.

Sunset Times are All Over the Place

What the four maps above obscure is the variation in sunrise and sunset times in a given place. The effect of daylight saving time is to keep the sunrise at about the same time in every place, while letting the sunset vary much more widely. The maps below show the variation in sunrise and sunset times—the number of hours between the earliest and latest sunrises and sunsets, in December and June—across the country.

While places farther north experience more overall variation, it’s very clear that sunrises are much more consistent than sunsets. The only exception, of course, is Arizona, which doesn’t observe daylight savings. There, sunrise and sunset vary by the same amount.

Reasonable Daylight Hours

A side effect of the extreme variation in sunset times is that for much of the year, the sun rises plenty early, but sets way too early. If we look at how many days have “reasonable” daylight hours—the sun is up before 8:30 a.m. and stays out until at least 6 p.m.—across the country, the results aren’t fantastic (left map below). Except for the far reaches of West Texas, there’s nowhere that has 8:30–6 daylight every day.

But if we were to switch to year-round DST (right map below), large chunks of the country would be guaranteed reasonable daylight, and the siutation would improve everywhere except northwest North Dakota. Thankfully, no one lives there.

The two maps above change a lot depending on how you define “reasonable” daylight hours, but the conclusion holds: unless you really care about early morning sunlight, we’d all be better off with year-round DST!