The concept of the "First 100 Days" refers to the early period of a U.S. president’s new term, typically seen as a symbolic window to set the tone, push key policies and demonstrate leadership. It represents a kind of political version of a first impression.

In the United States, no one talked that much about the importance of a president’s first 100 days—until Franklin D. Roosevelt took office in 1933. He took swift action to calm the nation’s crippling financial panic (cue the Emergency Banking Act and the “fireside chats” that became Roosevelt’s signature) and began rolling out the programs that made up his New Deal, including 15 major pieces of legislation in the first 100 days.

FDR’s extraordinary productivity translated into enormous popularity, and he set a first 100-day standard against which all future U.S. presidents would (perhaps unfairly) be measured.

John F. Kennedy ordered the ill-fated Bay of Pigs invasion 87 days into his presidency. At a time when the U.S. and the Soviet Union were locked in the Cold War, JFK’s first 100 days also saw the Soviets launch the first human into space.

September 1974, barely a month into his presidency, Gerald Ford gave Richard Nixon a full pardon for his involvement in the Watergate scandal that led to his resignation. Widespread condemnation of Ford’s decision to pardon his predecessor is thought to have contributed to his failure to win the 1976 election.

On Day 1, Ronald Reagan started off with a bang, announcing the release of U.S. diplomats being held hostage in Iran. Sixty-nine days into his administration, he survived an assassination attempt.

Barack Obama—who like FDR took office during a severe financial crisis—was able to get Congress to sign a $787 million stimulus package, the American Recovery and Reinvestment Act, on his 29th day in office.

Laws passed Most: Franklin D. Roosevelt – 76 Fewest: George W. Bush – 7

After FDR, Harry S. Truman comes in a respectable second place in this category, with 55 laws passed in the first 100 days after his 1949 inauguration. (Though Truman took office after Roosevelt’s death in April 1945, tallies of his first 100 days’ accomplishment usually start after he won election in his own right in 1948). Since then, presidents have gotten significantly less productive in the law-making department in their first 100 days (executive orders are another matter).

Foreign countries visited Most: Barack Obama – 9 Fewest: Dwight D. Eisenhower*, John F. Kennedy, Lyndon B. Johnson, Jimmy Carter and Donald Trump (tie) – 0

Obama is the clear winner in this category, visiting Canada, UK, France, Germany, Czech Republic, Turkey, Iraq, Mexico and Trinidad & Tobago in his first 100 days, according to the U.S. State Department’s Office of the Historian.

*Eisenhower did, however, make a visit to a combat zone in Seoul, Korea as president-elect in December 1952.

Approval rating after first 100 days Highest: John F. Kennedy – 83 percent Lowest: Donald Trump (first term) – 41 percent

Using data from the Gallup Poll, American Presidency Project recorded that despite such blunders as the Bay of Pigs invasion, Kennedy’s approval rating jumped significantly (11 points) during his first 100 days in office. Ronald Reagan’s jumped by even more at the outset of his administration, shooting from 51 to 68 percent. While presidential approval ratings generally tend to rise at the outset, Bill Clinton’s dropped three points during his first 100 days (from 58 to 55 percent), and so did Barack Obama’s (though his three-point drop brought him to a still respectable 65 percent, about average for new presidents since Eisenhower). During his first term, Donald Trump's approval rating was recorded at 41 percent.

Sources: FiveThirtyEight, American Presidency Project, CBS News, TIME, U.S. State Department Office of the Historian