The presidential inauguration happens every four years and is steeped in tradition, but not every part of the ceremony is set in stone.
Like taking the oath with a Bible. That was started by George Washington.
"Nowhere in the Constitution does it say you have to do that. It was his choice and only two other presidents have not done that: John Quincy Adams and Franklin Pierce," sad Gary Arndt, host of "Everything, Everywhere, Daily."
"Towards the end of the oath of office, Washington ad-libbed a line that said 'So help me God.' That is also not part of the oath of office," he said. "He just did it and that's something that's been a tradition ever since."
Arndt also pointed out that Inauguration Day wasn't always January 20. It used to be in March but was changed with the 20th Amendment.
And fun fact: anyone can facilitate the oath.
"By tradition, the Chief Justice of the Supreme Court is the one who inaugurates the president, but that doesn't have to be the case. Literally, you or I could do it."
And when it comes to when the oath is taken, that is all about precision.
"Within one minute of the stroke of noon is when the oath of office will take place," said Arndt.
"There's a big difference between 11:59 a.m. and 12 p.m., as far as who has decision-making abilities."
"There are literally people in the Pentagon and other places that are waiting for that moment to have the chain of command," Arndt said.
So if you're watching on Monday, you can expect to see Chief Roberts begin reading the oath of office at 11:59 a.m.