Donald Trump's presidential inauguration took place Jan. 20, as inaugurations have every four years since 1937, when the 20th Amendment made that the official date. While there's plenty of precedent for the ceremony, we've officially entered lots of uncharted territory as the reality star and semi-successful businessman becomes the 45th president of the United States. And as the nation is currently split over Trump's presidency — multiple polls find him the least popular incoming president of the past 40 years — some celebrities are using their platform to flex their American right to dissent.

Katy Perry, a long-vocal Hillary Clinton supporter, tweeted that she was "sleeping in," but "Then, I'm marching." Celebrities joining the DC Women's March to speak and attend also include America Ferrara, Ashley Judd (who is currently earning a Ph.D in public policy), Julianne Moore and Jessica Chastain.

Check out inauguration reactions from Katy Perry, comedian Michael Ian Black and more below:

 Celebrities Who Said No to Performing at Donald Trump's Inauguration