What Does the Military Have To Do With Daylight Saving and Other Military Time Traditions

By Danielle DeSimone

When thinking about daylight saving time – that is, adjusting time to obtain longer hours of daylight in the summer by setting the clocks an hour ahead of the standard time, and then setting them back again in the fall – many people misconstrue the practice’s origins and assume that its roots are in American farming hours.

But did you know that daylight saving time in the United States actually originated with the U.S. military? Here’s everything you need to know about what the military has to do with daylight saving time, and other military time traditions.

Daylight Saving Time Began in World War I

Daylight saving time was first observed on a large scale in 1918 in the midst of World War I. The Standard Time Act was signed into law to increase the number of daylight hours in a day, which not only extended the working day for war industries and factory workers, but also conserved fuel needed to operate those industries. The law was only in effect for just over a year and was repealed at the end of WWI.

Daylight Saving Time Returns in World War II, Coining the Phrase “War Time”

Decades later, just after the U.S. entered World War II, Congress once again passed a law in 1942 implementing daylight saving time in order to conserve fuel and “promote national security and defense.” The idea of changing time to assist in the war effort was so connected to WWII, in fact, that daylight saving time became commonly known as “war time.”

When WWII ended in 1945, just as in WWI, the law was repealed, and for approximately 20 years, the U.S. had no nationwide standard in terms of time, which caused a great deal of confusion. In fact, even the U.S. military – known for its promptness and dedication to being on time – was affected. Pentagon officials were late to a crucial military conference in Alaska because no one knew exactly what time it would be at their location when they arrived.

In both World War I and World War II, daylight saving time was used to increase working hours for war industries and factories, to assist with the war effort. This is why the practice became commonly known as “war time.” | Photo credit National Archives and Records Administration

Finally, in 1966, Congress passed the Uniform Time Act, establishing daylight saving time in all 50 states, aside from Hawaii and Arizona (with the exception of the Navajo Nation within the state), which do not observe daylight saving time.

Later in 2005, President Bush extended daylight saving by four weeks and since 2007, daylight saving has begun on the second Sunday of March and ends on the first Sunday of November.

Military Time Started with an Egyptian Sundial

Long before daylight saving time, ancient Egyptians and Mesopotamians established the 24-hour day. They used sundials to tell time during the day, and a water clock to tell time at night

The Egyptians followed a 24-hour-day structure, which is what we now call “military time” and is still utilized by the Armed Forces today to avoid confusion in communication when distinguishing between a.m. and p.m.

The Significance of “D-Day” and “H-Hour”

The military is also responsible for several time-related phrases. For example, did you know that the D-Day that famously occurred during WWII on June 6, 1944, is not the only D-Day in history? The term “D-Day” actually just refers to the day on which an important invasion or military operation will take place, and is not specific to that singular historical event.

When planning around this invasion or operation, military planners refer to the days preceding or following D-Day by adding numbers and a plus or minus to the “Day.” For example, “D-3” meant three days before a D-Day, whereas “D+7” means seven days after a D-Day operation.

Those planning these military operations also utilize a similar structure when discussing the details of timing on D-Day. “H-Hour” is used to refer to the hour in which operations for the D-Day operation begin. Much like D-Day, “H-3” means three hours before H-Hour and “H+7” means seven hours after H-Hour and the invasion has already begun. This way of planning is just one of the many ways the U.S. military utilizes time to conduct military operations.

The Military Has Longstanding Traditions for Crossing Time Zones and Geographic Lines

The U.S. military operates across the globe, with operations spanning multiple continents, oceans and time zones. For those in the Navy, these journeys include significant markers, such as when they cross through different time zones or across geographic lines.

Perhaps one of the most beloved, time-honored Navy traditions is that of “crossing the line” – when sailors aboard a ship crossed the equator for the first time in their Navy career.

These young sailors – referred to as “pollywogs” before their initiation – must go through a rite of passage, which has included physical challenges and often embarrassing tasks. These challenges are often full of mischief and all in good fun – and today, the tradition continues to mark a sailor’s accomplishment of being deemed a “shellback” – that is, a more experienced sailor who has crossed the equatorial line.