Repeatedly over the years, Gov. Tim Walz of Minnesota has said that the year he spent teaching in China began with a trip to Hong Kong during the pro-democracy protests in the spring of 1989 that culminated in the deadly crackdown that June in Tiananmen Square in Beijing.

As recently as February, Mr. Walz said on a podcast that he had been in Hong Kong, then a British colony, “on June 4 when Tiananmen happened,” and decided to cross into mainland China to take up his teaching duties even though many people were urging him not to.

Mr. Walz had told the same story a decade earlier, at a congressional hearing, when he testified that he “was in Hong Kong in May 1989,” adding, “As the events were unfolding, several of us went in. I still remember the train station in Hong Kong.”

But it was not true. Mr. Walz, the Democratic vice-presidential nominee, indeed taught at a high school in China as part of a program sending American teachers abroad, but he did not actually travel to the country until August 1989.

Contemporaneous news reports in Nebraska indicated that Mr. Walz was still in his home state during the spring and did not leave for China until August. And his campaign said on Tuesday that it did not dispute those accounts.

Mr. Walz’s version of events, which he related as a member of Congress in 2014 and has been repeated by his campaign staff and reported by The New York Times and other news organizations, put him close to the scene of one of the most dramatic episodes in modern history.

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