Answer: Inaugural day is a Federal holiday in the United States and marks the wwearing-in of President of the United States and other elected federal officials. The day is observed only by federal government employees in Washington, and certain counties and cities of Maryland and Virginia.
First Inaugural day was observed in 1793 and from 1793 till 1933, it was observed on March 4. However, 1933 ratification of the Twentieth Amendment changed the start date of the term of the president of United States. Now this event takes place on January 20, every fourth year, following Presidential election in United States. If January 20 is a Sunday, the president takes the oath on 20th only but Inaugural day is observed on January 21st.