On February 9, 1942, in the midst of World War II, President Franklin Roosevelt instituted year-round Daylight Savings Time (DST), called "War Time". War Time continued until the last Sunday in September 1945. 

After that, until 1966, there was no federal law on daylight saving time. This led to an era of confusing daylight-saving policies that differed by city, state, and municipality as well as by length. 

It was the transportation industry that began the push for federal regulation in 1962, given how confusing keeping timetables could be with all the different time zones. By 1965, eighteen states observed DST for six months out of the year, while another eighteen states did not have formal DST policies but had cities or towns in the state that kept to their own daylight saving standards. There were another twelve states that did not have DST at all that year. To make matters even more confusing, sections of North Dakota and Texas set their clocks back an hour instead of moving them forward, which made them off by as much as two hours from some other locations.

Finally, the Uniform Time Act of 1966 made its debut in a timely manner. It was put into practice in 1967, requiring clocks to advance one hour beginning at 2:00 a.m. on the last Sunday in April and turned back one hour at 2:00 a.m. on the last Sunday in October. 

At first, States that wanted to exempt themselves from DST could do so only if the entire state chose to do the same. This law was subsequently amended, allowing states split between time zones to exempt either the entire state or that part of the state lying within a different time zone.

DST is still up for debate, as reported by Rockland Daily here in 2023 and here in 2022, when legislation was advanced in support of the legalization of using daylight saving time as the year-round clock option. 

The effort in the 117th Congress to permanently extend “daylight savings time” (DST) came to an end, as the House of Representatives refused to act on the measure due, in large part, to the efforts of Agudath Israel of America presenting the unique and disruptive challenges permanent DST would create for the frum community.