Philadelphia Mayor Cherelle L. Parker privately took the oath of office ahead of her official inauguration Tuesday

Philadelphia Mayor Cherelle L. Parker privately took the oath of office Monday ahead of her official inauguration ceremony Tuesday, according to a source with knowledge of the situation.

Under city law, Parker, the first female mayor in city history, officially became mayor at midnight. But she is not being publicly sworn in until her inauguration ceremony Tuesday because City Council, which hosts the ceremony during a special meeting, scheduled the event to avoid conflicting with the Mummers Parade on New Year’s Day.

WHYY first reported that Parker was privately sworn in. A source confirmed to The Inquirer Monday that Parker took the oath of office.

Parker spokesperson Joe Grace would not confirm Parker took the oath, saying only that “there was a legal step taken.”

“She became mayor by force of law,” Grace said. “She is mayor, and that didn’t change. But our focus is on the public administration of the oath of office tomorrow morning, for all of Philadelphia to see.”

» READ MORE: The Mummers Parade will delay the next mayor’s inauguration

Under the Philadelphia Home Rule Charter, a document akin to a constitution, a new mayor takes office on the first Monday in January, which happened to coincide with New Year’s Day this year.

The charter also says that elected officials must take the oath of office “before entering upon the duties of their office or employment.”

Mayors usually take the oath during the Council session about 12 hours after they technically became mayor. During that time, the city continues to function in the status quo and with leaders who served under the previous administration. In this year’s case, the gap between when Parker officially took office and her scheduled public swearing-in would have been about 36 hours.

City law does not require the oath to be administered in public — only that there is at least one witness.

Parker’s inauguration ceremony will take place at The Met Philadelphia, the concert hall inside the historic former opera house on North Broad Street. City Council members and row office holders will also be sworn in, and Council is expected to elect Kenyatta Johnson its next Council president.

The new mayor is also scheduled to attend a swearing-in ceremony Tuesday afternoon for incoming Police Commissioner Kevin J. Bethel.

Inquirer staff writer Lizzy McLellan Ravitch contributed to this article.