Judging from his comments and tweets, Donald Trump is a leader who divides the sweep of human history into two simple categories: BT (Before Trump) and AT (After Trump).

Before Trump, there was mostly a void populated by a few military heroes like Andrew Jackson and George Patton.

That nearly empty mental landscape is on display every time the president is forced to acknowledge the 19th century. Not only did Trump appear to believe that Frederick Douglass was a contemporary figure (“an example of someone who has done an amazing job”), but he also seemed startled to learn that Abraham Lincoln was a Republican (“A lot of people don’t know that”).

OK, many Americans have trouble keeping Millard Fillmore and Rutherford B. Hayes straight in the pageant of the American presidency. But what distinguishes Trump from almost anyone else in government is his shaky grasp of public events after his birth in 1946.

As our second-oldest president at 71, Donald Trump has been around for nearly one third of the history of our constitutional democracy. During Trump’s lifetime, 12 other presidents (beginning with Harry Truman) have occupied the Oval Office, and America has waged five major wars (Korea, Vietnam, the Gulf War, Afghanistan and Iraq).

So to steal a book title from Hillary Clinton, Trump has been “Living History.”

But most of it eluded Trump during his starlet-studded rise through New York real estate and reality television. Before becoming president, Trump’s biggest historical quest was his bogus search for the nonexistent evidence that Barack Obama was born in Kenya.

If Trump had been paying even a dollop of attention to major news events in his lifetime, he would be — despite his many other flaws — a better president. Here’s what Trump missed:

1962: The future president was attending New York Military Academy when America teetered on the brink of nuclear war during the Cuban missile crisis. If one lesson emerged from John Kennedy’s handling of the eyeball-to-eyeball confrontation with Nikita Khrushchev, it was that carefully chosen words are crucial in defusing a crisis that could end with a mushroom cloud.

Contemporary moral: Twitter Man should be extremely cautious that he does not dangerously provoke Rocket Man in North Korea.

1968: Trump was weeks away from collecting his undergraduate business degree from the Wharton School when Martin Luther King Jr. was assassinated. One week after King’s death, Congress passed the Fair Housing Act.

Then, in 1973, Trump and his father were charged with violating the housing law by practicing racial discrimination in the renting of apartments. With aid of snarling attorney Roy Cohn — who got his start as Joe McCarthy’s henchman — the Trumps signed a consent decree with the government in 1975.

Contemporary moral: Trump should have learned from the fair-housing case about the prevalence of discrimination. And the King assassination was a reminder that racial hatred is still embedded in the fabric of the nation — and a president should never encourage the forces of intolerance.

1973: Last Friday was the 44th anniversary of the Saturday Night Massacre, when Richard Nixon orchestrated the firing of Watergate special prosecutor Archibald Cox. More than any single event, that heavy-handed Nixonian effort to obstruct justice galvanized the House Judiciary Committee to seriously consider (and ultimately vote for) impeachment.

Contemporary moral: Robert Mueller, please pick up the white courtesy phone.

1983: In an address on the risks of accommodating the Soviet Union, Ronald Reagan warned of the temptation “to ignore the facts of history and the aggressive impulses of an Evil Empire.” At the time of the Reagan “Evil Empire” speech, Vladimir Putin was a KGB intelligence office in East Germany.

Contemporary moral: More than a quarter-century after the Soviet Union disintegrated until Mikhail Gorbachev, the aggressive impulses of Putin’s Russia have emerged as a throwback to the Communist era. Trump’s dismissal of Russia’s meddling in the 2016 election is akin to an American peacenik arguing in 1983 that the Cold War was entirely the fault of U.S. militarism.

1986: A horrified nation watched on television as the Challenger space shuttle blew up 73 seconds after its launch from the Kennedy Space Center. Less than six hours later, Reagan went before the nation (with words hastily written by Peggy Noonan) with probably the most moving speech of his presidency.

The lines that resonate most were addressed to the nation’s school children: “I know it is hard to understand, but sometimes painful things like this happen. It’s all part of the process of exploration and discovery. It’s all part of taking a chance and expanding man’s horizons.”

Contemporary moral: Reagan understood that to offer consolation from the Oval Office meant that his words had to speak to the emotional needs of children and families — and not the ego needs of the president himself.

2001: Six days after the 9/11 attacks, George W. Bush visited the Islamic Center in Washington. At a moment of fear and rage, Bush spoke about the need to treat Muslims in America “with respect” and said women who cover their heads “must not be intimidated in America.”

Contemporary moral: During the 2016 campaign, Trump falsely claimed that he had seen Muslims in New Jersey celebrate the toppling of the Twin Towers. In contrast — at a moment when scapegoating all Muslims would have been popular — Bush courageously recognized that America’s tolerance and diversity are among our greatest strengths in an age of terrorism.

Certainly, Trump’s lifetime has been riddled with disastrous presidential mistakes from Vietnam to Iraq. But there have also been moments of glory that Trump might have noticed if he had not been obsessed with his money, his career and his ego.