Clinton will begin Sunday morning at Ground Zero in Manhattan, participating in an annual moment of silence at 8:46 a.m. ET to mark the moment the first plane hit a World Trade Center tower.
She won't speak and is going to pay her respects -- not in a campaign capacity -- her aides said.
Despite the one-day reprieve, both Clinton and Trump have made 9/11 major themes of their campaigns, each speaking vividly about the aftermath of the attacks and the United States' actions since.
In January, when GOP primary rival Sen. Ted Cruz attacked "New York values," Trump recalled 9/11 vividly in a debate.
"It was with us for months, the smell," Trump said. "And everybody in the world loved New York, loved New Yorkers -- and I have to tell you, that was a very insulting statement."
Clinton was at Ground Zero on the day after the attacks and worked in the Senate to bring billions of dollars in aid for first responders and rebuilding efforts to New York City -- a role she has touted on the campaign trail.
"I was a senator from New York," Clinton said Tuesday in Tampa. "I knew people who were killed. I worked with families and the few survivors. I worked to get the health care needed by our first responders and emergency workers who ran toward danger. I worked to make our country safer and to rebuild New York and the Pentagon."
They also have used the aftermath of the history-changing attacks to push their case for why they should be the next commander in chief.
Trump claimed Thursday at a charter school in Cleveland that he would have caught Osama bin Laden prior to the 9/11 attacks he masterminded.
"I would have been tougher on terrorism," Trump said. "Bin Laden would've been caught a long time ago, before he was ultimately caught, prior to the downing of the World Trade Center."
Clinton, meanwhile, often recalls being in the White House Situation Room with President Barack Obama the day he green-lit the mission that led to the killing of bin Laden, saying the moment underscores her experience with tough security decisions and shows why she's ready to be in the Oval Office.
"When it came time to go around the table, with extremely experienced, thoughtful experts, we all gave our opinions. I was one who said I thought it was worth the risk," Clinton said Thursday in Tampa.
It's long been a prominent portion of Clinton's stump speech. She told an Iowa crowd in January it was "one of the most tense days of my life."
And they also use the policies that 9/11 spawned to take the each other down.
At an event Thursday, Clinton described Navy SEALs removing women and children from bin Laden's compound. "That, Donald Trump, is what American honor looks like," she said.
Trump, meanwhile, has made his opposition to the Iraq War, launched under President George W. Bush in the wake of the 9/11 attacks, a core foreign policy talking point.
Trump has repeatedly claimed he opposed the Iraq war from the beginning, even though he supported it in a 2002 interview with Howard Stern and didn't make any public comments opposing the war before it began. He's cited Clinton's vote in favor of it as evidence of her poor decision-making ability.
"Had I been in Congress at the time of the invasion, I would have cast a vote in opposition," he said Thursday in Cleveland.
But both candidates plan to pause those efforts to persuade voters on the 15th anniversary of the 9/11 attacks.
The tradition of presidential candidates shutting their campaigns down for the anniversary of the 9/11 attacks began in 2004, with President George W. Bush and Democratic challenger John Kerry.
In 2008, then-Sen. Barack Obama and Sen. John McCain held a joint event at Ground Zero. And in 2012, Obama and Mitt Romney suspended their negative advertisements and held separate events focused on 9/11 and military service.
This election, the day has even more resonance for the candidates, since both parties' nominees are New Yorkers.
At the same time, their personal ties to the sensitive historical event haven't kept Trump and Clinton free from controversy on the subject.
In a November debate against Democratic primary rival Bernie Sanders, Clinton invoked the 9/11 attacks and her tenure as a New York senator, from 2001 to 2009, to fend off charges from the Vermont senator that she was too close to Wall Street.
The comment -- connecting 9/11 with campaign finance -- infuriated liberals, with Sanders saying the next day that he had "no idea what the connection is" and another candidate, former Maryland Gov. Martin O'Malley, calling it "a pretty disgraceful moment."
One week later, Trump set off a bigger controversy with a claim he made at a rally in Birmingham, Alabama.
"I watched when the World Trade Center came tumbling down," he said. "And I watched in Jersey City, New Jersey, where thousands and thousands of people were cheering as that building was coming down. Thousands of people were cheering."
Local police said Trump's claim was wrong, fact-checkers disputed it and Trump's campaign never produced any evidence to support it.
Still, Trump stood by it the next day in an interview with ABC "This Week" host George Stephanopoulos, saying, "It was on television. I saw it."
"There were people that were cheering on the other side of New Jersey, where you have large Arab populations. They were cheering as the World Trade Center came down," Trump said.
Trump was pilloried by his rivals for the comment. Former New York Gov. George Pataki, at that time a primary rival, tweeted that he wasn't sure "what luxury spider-hole" Trump hid in on 9/11, "but I saw Americans come together that day."