Former New York mayor and current Donald Trump campaign surrogate Rudy Giuliani took the stage in Ocala, Florida, on 12 October 2016 and launched into a 10-minute diatribe against Hillary Clinton, maintaining (among other accusations) that Clinton had lied when she said she was in New York City on 11 September 2001, the day terrorist attacks were launched on the World Trade Center.

Accusing Clinton of neglecting her constituents after the collapse of the World Trade Center towers, Giuliani averred that she had fibbed about being in New York that day:

“Don’t tell me, if you said that, that you remember Sept. 11, 2001. I remember Sept. 11, 2001. Yes, yes, you helped to get benefits for the people that were injured that day. But I heard her say one day she was there that day. I was there that day. I don’t remember seeing Hillary Clinton there. That was like when she said she had to run through gunfire. That turned out to be, what do we call it? A lie.” Rudy Giuliani: "I was there" on 9/11, "I don't remember seeing Hillary Clinton there." https://t.co/iRB09cQ8eH — ABC News Politics (@ABCPolitics) October 12, 2016

Giuliani was soon chagrined when photographs of Senator Clinton walking right next to him through the streets of New York City in the immediate aftermath of the 9/11 attacks quickly surfaced on the Internet:

Giuliani was literally correct in the sense that Senator Clinton was in New York City on 12 September 2001, the day after the attacks, and not on 9/11 itself. (The shutdown of air traffic and the closure of transportation systems in the immediate aftermath of the attacks would have made a same-day journey extremely difficult.)

When confronted with the evidence, Giuliani acknowledged his mistake and offered an apology:

[F]ormer New York Mayor Rudy Giuliani told a crowd that Hillary Clinton had falsely claimed to have been in New York on Sept. 11, 2001 — an incorrect claim he took back a few hours later. “I made a mistake. I’m wrong and I apologize,” Giuliani [said]. On many occasions, Clinton has described being in Washington, D.C., on Sept. 11 when hijacked jets struck the World Trade Center and the Pentagon. She was a member of the Senate at the time, and Congress was in session. The next day, commercial flights remained grounded but Clinton traveled to New York City aboard a government plane. There, she circled the smoldering World Trade Center in a helicopter, then toured ground zero with Giuliani and New York’s Republican governor, George Pataki. Photos of that tour show Clinton standing shoulder to shoulder with Giuliani. Asked about his comments, Giuliani said he thought he had heard Clinton say during the last presidential debate that she was in New York on 9/11. But after being contacted by a reporter, he reviewed a transcript and found out he was wrong. Told that he was being criticized online by people posting photographs of him with Clinton at ground zero, Giuliani was contrite. “I probably deserve it,” he said.

Although she didn’t say so during any of the 2016 presidential debates, Clinton did reference having been in New York City on 9/11 on at least one occasion: