What to know about a national day of mourning for former President Jimmy Carter

American flags at federal institutions will remain at half-staff past the swearing-in of Donald Trump as the nation's 47th president to honor its 39th, Jimmy Carter, who died Sunday at the age of 100.

President Joe Biden declared Jan. 9 a national day of mourning for Carter, who was elected to a single term in 1976.

Biden ordered the flags to fly at half-staff for 30 days. 

It's a rare moment, when the nation stops to honor the life of a president — and one that historians point out is not codified into law.

"It’s been different for different presidents," said Alan Singer, a historian and professor of education and director of social studies education at Hofstra University.

What is a national day of mourning

Around the world, national days of mourning are generally reserved to honor the death of a head of state or the victims of a mass casualty incident. The most recent national day of mourning in the United States occurred after the death of former President George H.W. Bush in 2018.

"There are no official criteria" for what constitutes a nationwide time to mourn or another symbolic nationwide pause, Singer said. He noted that a handful have been declared in modern American history for incidents besides the death of a president.

"9/11 and Hurricane Katrina were tragedies," Singer said, referring to the events then-President George W. Bush declared as a national day of mourning and a national day of prayer and remembrance, respectively.

In 1968, Singer said, President Lyndon B. Johnson declared national days of mourning for both Martin Luther King Jr. and Robert F. Kennedy because "they were national leaders who were assassinated."

What's the history behind the honor in the United States?

The tradition dates back to the death of President Thomas Jefferson in 1826, according to Singer, when President John Quincy Adams issued an executive order calling for the flag to be flown at half-staff, among other honors.

The next three presidents for which a day of mourning was observed — Abraham Lincoln, James A. Garfield and William McKinley — were all assassinated, Singer noted. The next two presidents given the honor — Warren G. Harding and Franklin D. Roosevelt — died while in office, he said.

How will Carter be honored on Jan. 9?

Biden ordered that Carter receive a state funeral, a multiday, three-stage affair usually reserved for heads of state and organized by the U.S. military.

Carter will lie in state at the Carter Center in Atlanta for public visitation from Saturday evening through the morning of Jan. 7. He will next lie in state in the Capitol Rotunda in Washington, D.C., through the morning of Jan. 9, according to the Joint Task Force-National Capital Region website.

That morning, a motorcade will transport Carter’s remains to the Washington National Cathedral before a final flight and ground transport to Maranatha Baptist Church in Plains, Georgia, where a private funeral service is scheduled ahead of a private interment, according to the Joint Task Force-National Capital Region.

Biden said Carter had asked him to deliver his eulogy upon his death.

What is closed on Jan. 9?

In an executive order issued Monday, Biden announced "all executive departments and agencies" of the federal government would close Jan. 9. However, some agencies and federal employees may operate and report for duty as normal "for reasons of national security, defense or other public need," according to the order.

Chief Justice John G. Roberts ordered the Supreme Court closed Jan. 9, according to a statement.

The New York Stock Exchange announced it would be closed Jan. 9 in a statement. Nasdaq similarly announced it would close its U.S. equities and options markets.

All retail locations of the United States Post Office will be closed Jan. 9 and there will be no mail delivery, according to a spokesperson for the Postal Service.

The postal agency halted regular mail deliveries and office activities on Dec. 5, 2018, the national day of mourning for former President George H.W. Bush, according to a statement dated two days before that closure.