Five hundred and thirty-eight people will convene in various places around the US on Monday (Dec. 19) to officially elect the country’s next president and vice president.

While usually considered a mere post-election formality, the vote has drawn unprecedented attention and anxiety this year—because of the chance, however small, that Donald Trump could end up not being president after all. Pressures for the electors to turn “faithless” and overturn his win have been mounting from the anti-Trump camp: Hillary Clinton won the popular vote, after all, and it was recently revealed that Russia tried to intervene in the election in Trump’s favor. For the presidency to slip away from Trump, at least 37 Republican electors would have to change their minds on Dec. 19.

But even though the formal electoral vote happens Monday, the results won’t be known for several weeks. When exactly? Not until Jan. 6, 2017.

According to the United States Code, provision 15 of Chapter 1 of Title 3:

Congress shall be in session on the sixth day of January succeeding every meeting of the electors. The Senate and House of Representatives shall meet in the Hall of the House of Representatives at the hour of 1 o’clock in the afternoon on that day, and the President of the Senate shall be their presiding officer.

Vice president and Senate president Joe Biden will supervise as lawmakers gather to tally the Electoral College’s votes that day. Barring any challenges raised, Biden will then declare the official winner of the election based on who gets the majority of votes—at least 270. (Three times in history, this setup has resulted in the sitting vice president awkwardly announcing his own defeat, the New York Times notes, as an aside.)

The president is then officially sworn into office on Jan. 20.