Daylight Saving Time: Why It Exists and How It Affects You

Twice a year, much of the world goes through the ritual of adjusting every clock by one hour — moving them forward in spring and backward in autumn. Daylight saving time is so deeply embedded in many countries' calendars that most people follow it without thinking about where it came from or why it still exists. The history, the mechanics, and the ongoing controversy around it are more interesting than most people realize.

The popular story credits Benjamin Franklin with inventing daylight saving time based on a satirical 1784 essay he wrote suggesting Parisians could save money on candles by waking up earlier. But the essay was a joke, not a serious proposal. The actual first serious proposals came from New Zealand entomologist George Hudson in 1895, who wanted more evening daylight to collect insects, and British builder William Willett in 1907.

Germany became the first country to officially adopt daylight saving time in 1916 during World War I as a coal-saving measure — if people were awake during more daylight hours, less artificial lighting would be needed. Britain followed shortly after, and the practice spread to many countries over the following decades. After World War I, most countries abandoned it, then revived it during World War II for the same energy-saving reasons.

In the United States, daylight saving time became standardized by the Uniform Time Act of 1966, which established when clocks would change nationwide. Individual states can opt out — Arizona (except the Navajo Nation) and Hawaii do not observe daylight saving time. Since 2007, the U.S. has observed it from the second Sunday of March to the first Sunday of November.

The claimed energy savings that originally justified daylight saving time are now disputed by research. Studies of regions that changed their observance found that while evening lighting use dropped, morning heating use increased — largely offsetting the savings. Some studies found a net increase in energy consumption in warmer climates, where the extra evening daylight caused more air conditioning use.

The health effects of daylight saving transitions are better documented and consistently negative. The Monday after spring forward is associated with a significant increase in heart attacks, strokes, and traffic accidents — all linked to sleep deprivation from losing one hour. The economic cost of reduced productivity in the days after the spring transition has been estimated in the billions of dollars.

A growing movement supports eliminating seasonal clock changes entirely — either staying on standard time permanently or making summer time permanent year-round. The EU voted in 2019 to eliminate the biannual clock changes, but implementation has been delayed due to disagreements about which time to adopt. Multiple U.S. states have passed legislation to adopt permanent daylight saving time, contingent on federal approval.

Regardless of where you fall on the political debate, the practical reality is that daylight saving time affects your schedule, your sleep, and your coordination with people in other regions. GoClasstime's world clock automatically accounts for daylight saving transitions, always showing the correct current time for each city regardless of whether daylight saving is in effect.