From the Introduction: "Since the 20th Amendment was ratified, the oath of office for President of the United States has been administered every four years at noon on January 20. In 2021, the President- and Vice President-elect are to be officially sworn in at noon on Wednesday, January 20. Planning for the 2021 inauguration is being challenged by the Coronavirus Disease 2019 (COVID- 19) pandemic; adjustments to traditional ceremonies, customs, and practices are being made. This In Focus presents information related to 2021 inauguration security and operations based on past inaugural activities and announced activities to date."
CRS In Focus, IF11710
Congressional Research Service: https://crsreports.congress.gov/