Why do we observe daylight savings time?

Ahh, falling back. Daylight Savings Time ends at 2:00 a.m. on November 3, 2013, when people in many parts of the world will turn clocks back to 1:00 a.m. for a bizarre do-over of 1:00 a.m. to 2:00 a.m. that day. Even as we remember the sting of springing forward, “getting an extra hour” in the morning feels sooooo good.

Image courtesy quinndombrowski.

But the rationale for Daylight Savings Time is not to gain that extra hour of sleep in the fall. It’s for that extra hour of daylight in the summer. During summer months, some parts of the world advance their clocks one hour to maximize evening daylight hours, in theory saving energy required to light evening activities before bed.

Kind of crazy, until you realize that historically, many societies depended so heavily on the sunlight that they measured the day in unequal hours (e.g. Talmudic hours), where an hour meant a certain fraction of the daylight–anywhere from 44 to 75 minutes long, depending on the season.

Thinking about time as a social and legal construct makes my head hurt a little bit. It made 20th Century America’s head hurt a little bit, too. In the United States, the Standard Time Act of March 19, 1918 established standard time zones and the first observance of Daylight Standard Time as an energy saving effort. Daylight Standard Time was unpopular and was abolished until World War II, when it enjoyed another nationwide stint from 1942-1945. Since 1945, the question of whether to observe Daylight Savings Time has been up to the states. Although the 1966 Uniform Time Act expressly superseded state laws, the Act allowed leeway for 1) entire states or 2) entire portions of a state within a given time zone to exempt themselves from Daylight Savings Time. Arizona, Hawaii, Puerto Rico, and the U.S. Virgin Islands do not observe Daylight Savings Time.

Native nations are free to observe or not observe Daylight Savings Time. The Navajo Nation in Arizona, for example, observes Daylight Savings Time. The Hopi Reservation does not, despite being surrounded by the Navajo Nation. In fact, in Tuba City, AZ, the time zone can change across the street.