Daylight Savings Time 2013: Why Arizona doesn't observe Daylight Saving

PHOENIX - It's that time again -- but not for Arizona.

This upcoming weekend marks the beginning of Daylight Saving time for most of the United States.

However, unlike almost everywhere else, Arizona doesn't observe Daylight Saving Time (DST), and hasn't done so for about the last 40 years.

We'll explain why that's the case in a minute.

If this weekend seems earlier than normal for DST, you're right. In 2007, President Bush signed into law an energy bill that called for Daylight Saving Time to begin three weeks earlier, on the second Sunday in March, and end one week later on the first Sunday in November.

Prior to 2007, DST started on the first Sunday in April and ended on the last Sunday in October.

Arizona's independence from this annual time change can cause a lot of confusion for residents and visitors alike.

It means the state is in the same time zone as Denver from November to March, but then falls behind Denver to Los Angeles time from March to November.

Why doesn't Arizona change? It has a lot to do with the weather.

The history of daylight saving is tied to energy conservation. Switching to DST in the summer means more sunlight at night, which in turn means homes don't have to turn on lights as early.

According to the U.S. Government , that leads to energy and fuel savings.

Over the course of the last 100 years, the United States (including Arizona) has gone on Daylight Saving time in both World War 1 and World War 2, but then gone off after the wars were over.

In 1973, a more permanent federal law was enacted to help with the oil shortages of that time. But Arizona asked for – and was eventually granted an exemption.

According to an Arizona Republic editorial from 1969, the reason was the state's extreme heat. If Arizona were to observe Daylight Saving Time, the sun would stay out until 9 p.m. in the summer (instead of 8 p.m., like it does currently).

"[Data] clearly show that we must wait until about 9 p.m. DST to start any night-time activity such as drive-in movies, moonlight rides, convincing little children it’s bedtime, etc," the editorial stated. "And it’s still hot as blazes!"

Another Arizona Republic editorial from 1968 stated, "Drive-in theaters, the parents of small children, the bars, the farmers and those who do business with California" were against Daylight Saving time while "power companies, the evening golfers, the late risers, and the people with business interests on the Eastern seaboard" were for it.

But don't be fooled by Arizona's DST stance. Not every corner of Arizona is exempt from Daylight Saving Time today.

The Navajo Indian Reservation follows DST, but the reservation stretches across four different states.

If all of Arizona were to re-evaluate its stance and choose to observe DST, here's what would change.

Instead of sunrise at 5:30 a.m. during most of the summer, the sun would come up at 6:30 a.m. And at the end of the day, the sun would set at 9 p.m. instead of 8 p.m. Winter sunrise and sunset times would remain the same.

A 2009 Michigan State University published by the American Psychological Association study showed that DST has adverse effects on the American workplace.

"Following [the start and end of DST], employees slept 40 min less, had 5.7% more workplace injuries, and lost 67.6% more work days because of injuries than on non phase change days," explained the study, which looked at mining injuries between 1983 and 2006 from the National Institute for Occupational Safety and Health.

Daylight Saving Time starts at 2 a.m. local time Sunday, March 10, 2013. It ends on November 3, 2013.