Joshua and Hannah Bowman were driving through northeast Arizona on a cross-country road trip a few years ago, after deciding to move to California from Massachusetts. They had left Four Corners, safely taking U.S. Route 160 as evening rolled in, when something strange started happening on their phones.

“We saw that we were changing time zones fairly quickly,” Bowman said. “The twilight added a little bit to the mystery.”

Without knowing it, they had entered the Daylight Saving Doughnut.

[Read how daylight savings affects your health]

It’s that time again — daylight saving time ends at 2 a.m. Sunday, when clocks are turned back one hour. And while most people in the United States get to enjoy an extra hour of sleep, confident their phones will attend to the task of winding back the clock, two states — Arizona and Hawaii — will not “fall back” because they did not “spring forward.”

But what does that have to do with doughnuts?

OK, not all of Arizona holds out on daylight saving. In the northeastern quarter of the state, the Navajo Nation observes the time change in the spring.

But the Hopi Nation, which is encircled by Navajo territory, does not, making it the figurative “doughnut hole.”

The Navajo Nation is semiautonomous, with the power to set its own time system. Since the Navajo reservation extends into neighboring states that recognize daylight saving time — Utah and New Mexico — the nation decided to follow suit to keep the same time throughout its land.

“That means every summer, you have the Hopi Reservation with standard time, surrounded by the Navajo Reservation with daylight time, surrounded by the state of Arizona in standard time,” said David Prerau, a time policy expert and the author of “Seize the Daylight.”

“It is a very interesting, and confusing situation, and they’ve had that for years.”

The time change on Sunday brings everyone to standard time.

Who decided the rules for daylight saving time to begin with?

To understand how we got to where we are, we have to turn back time to the years after World War II, when there was no uniform national system.

At one point, there were 23 different pairs of daylight saving start and end dates in the state of Iowa. There was also a bus route that ran between Moundsville, West Virginia, and Steubenville, Ohio, that saw passengers changing time zones seven times in only a 35-mile stretch.

“Anybody could do what they wanted,” Prerau said. “You had a lot of unusual circumstances.”

But in 1966 Congress established the Uniform Time Act, which standardized daylight saving time across the country. Any state could exempt itself, and Arizona opted out of the law in 1967.

Why did Arizona get rid of it?

If you ask an Arizonan, they’ll probably tell you it’s all about energy conservation.

“It’s not unique to Arizona culturally, it’s more geographic,” said Calvin Schermerhorn, a professor of history at Arizona State University.

Arizona’s most populated areas, around Tucson and Phoenix, are very, very hot in the summer, and an extra hour of daylight to stay outdoors was not an incentive. Rather, the best time to go outside is often after the sun goes down.

“Instead of saving fuel, daylight saving time saw more fuel being spent on air conditioning, because of the extra hour of daylight” at the end of the day, Schermerhorn said.

But even now, there are those who would rather see Arizona follow daylight saving time. Many issues arise while traveling to, from or through the state. Businesses have complained of difficulties coordinating with their national or global branches. Communication is a problem, with many missed calls.

“It puts Arizona out of sync with everybody else,” Prerau said.

Are any other states going to make the change?

Hawaii’s choice against observing daylight saving time causes less disruption than Arizona’s given that it is isolated from other states and near the Equator, where the sunrises and sunsets don’t vary much.

Several overseas territories, including American Samoa, Guam, Northern Mariana Islands, Puerto Rico and the U.S. Virgin Islands also do not observe daylight saving time.

And many other states are pushing to drop daylight saving time all together. Over the past few years states including Ohio, Illinois, Michigan, Alaska, Texas, Utah and Washington have pushed back against daylight saving time.

But others have fought to permanently stay in daylight saving time. Proposals have been filed in Florida, Idaho, Oregon and New Mexico.

“We’re marching away from that uniformity, which could wreak havoc on all the systems that rely on synchronized time,” Schermerhorn said.

There is support for getting rid of the time changes. Seven in 10 Americans would rather not have to switch their clocks twice a year, according to a poll by The Associated Press-NORC Center for Public Affairs Research released this past week.

What is less clear is whether they want to stay on standard time year round, or daylight time. Four in 10 Americans would like to stay on standard time, the poll found, while about three in 10 prefer full-time daylight time.

Even if everyone was on the same page with daylight saving, there would still be temporal fissures across the nation, with 14 states split by two different time zones. There are even some instances of towns which recognize time zones unofficially, such as Kenton, Oklahoma, in the western edge of the Panhandle. Officially, it’s on Central Time, but the town informally follows Mountain Time to be in sync with New Mexico, which is only 3 miles away.