The 100-day standard is not much of a guide to the future success of failure of a presidency. Ronald Reagan signed his signature tax cuts into law on his 206th day in office; President Obama signed what would be known as Obamacare on the 368th day of his first term; and JFK’s stellar performance in the Cuban Missile Crisis came after his 634th day in office.
Until the first part of the 20th century, when an historian, journalist or politico used the term “Hundred Days,” they usually meant Napoleon Bonaparte’s ill-fated frenetic activity from the time he escaped from Elba in 1815 until his permanent fall from power after the military defeat at Waterloo. As for American precedents there is no evidence that George Washington, who was well aware that he was establishing the basic norms of the new American presidency, thought there was anything significant about his first 14 weeks in office. It was the actions of Franklin Delano Roosevelt and the 73rd Congress in 1933 that turned the meaning of the concept on its head, making it a symbol of executive success.
As historian Arthur Schlesinger—whose hugely influential “The Coming of the New Deal” (1959) chiseled the concept of “The Hundred Days” into historical marble—noted, Roosevelt himself did not come into office thinking there was something magical about his first 100 days as president. What he knew was that action was required to calm American fears and stabilize the financial system. Using a constitutional power intended for use in a national emergency, the president called Congress back for a special session. Five days later, after another presidential proclamation announcing a bank holiday and passage of the Banking Bill, Roosevelt thought he had done enough for the moment.