(This story has been updated with additional information.)
President Donald Trump's second administration will mark one of its first big milestones on April 30 when it hits its 100th day in office - a moment to take stock of the new commander-in-chief's progress. But how did the seemingly arbitrary metric even become a thing? It all started with President Franklin Delano Roosevelt, the nation's 32nd president.
Roosevelt, who took office in 1933 and steered the U.S. economy through the Great Depression and World War II, ushered in the first phase of the New Deal within his first 100 days. Based on the promise that the federal government was needed to lift the nation out of the depths of economic collapse, he quickly authorized the passage of banking reforms, emergency work and agricultural programs.
The Trump administration has focused the first 100 days of its second term on fulfilling campaign promises, which include reducing the size of the federal government by establishing the Department of Government Efficiency. The administration has also issued several executive orders aimed at targeting perceived adversaries, leading to the demotion or firing of numerous officials, prosecutors and FBI agents who worked on investigations related to the president and the Jan. 6, 2021, attack on the U.S. Capitol.
Here's how an administration's first 100 days became an unofficial landmark in a presidential term.
Roosevelt did not assume office to make the first 100 days a benchmark for his presidency, according to historian Arthur Schlesinger, the author of "The Coming of the New Deal."
"Roosevelt had first thought of putting through the emergency banking legislation and sending Congress home," Schlesinger wrote.
However, the depths of the Great Depression and a favorable Congress gave Roosevelt the political environment to move quickly.
The 73rd Congress passed 15 major pieces of legislation during Roosevelt's first 100 days that established key parts of the New Deal, including:
In his first 100 days, Roosevelt's achievements created an informal landmark in a new president's term that has become a burden to some administrations and a rallying cry for others, even if they acknowledge the difficulty of meeting Roosevelt's standard.
"All this will not be finished in the first 100 days," John F. Kennedy said in his inaugural address. "Nor will it be finished in the first 1,000 days, nor in the life of this administration, nor even perhaps in our lifetime on this planet. But let us begin.
Presidents Dwight D. Eisenhower and Richard Nixon downplayed the 100-day mark, according to History.com. Other presidents have embraced the comparison to Roosevelt.
President George W. Bush convened a luncheon with members of Congress on his 100th day in office, CNN reported, and told ABC that his opening weeks "laid a foundation for some serious change in Washington."
In 2009, then-President Barack Obama held a news conference on his 100th day in office to outline his achievements and set the tone for the remainder of his term.
"I think we're off to a good start, but it's just a start," Obama said in his opening remarks. "I'm proud of what we've achieved, but I'm not content. I'm pleased with our progress, but I'm not satisfied."