At noon on January 20 of the year immediately following the Presidential election. Inauguration Day used to be March 4, but the Twentieth Amendment changed the date in 1937, during Franklin D. Roosevelt's second term.
The Chief Justice is head of the US Supreme Court, which is head of the Judicial Branch of government, so the choice of official is appropriate and traditional, but not required. The President may select someone else to issue the Oath of Office if he (or she) so desires.
judicial, executive
The President of the U.S. is the Commander-in-Chief of the Armed Forces. Yes, he could issue such an order.
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As commander in chief, he can issue executive orders to make changes to military protocol itself
Chief Justice John Marshall and the Court gave up the power to establish courts and to issue writs of mandamus.
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The main power of the executive branch of the government is to carry out laws. The president is the Commander in chief of the armed forces The president appoints supreme court justices The president can issue executive orders The president can veto bills
the president's authority as commander in chief
Zachary Taylor was only President for a year; he died in office in 1850. The Galphin Affair was an estate issue that involved one of his Cabinet members
which Pakistan provincial chief minister was dismissed on the issue of one unit
The fifteen US executive departments are Treasury, Commerce, Homeland Security, Agriculture, Education, Defense, Housing and Urban Development, Health and Human Services, Labor, State, Energy,Veterans Affairs, Interior, Transportation and Justice. In most cases the function of each department is clear from its name. Interior deals with such things as national parks and forests, wildlife preservation areas, waterways ,water rights, and Indian affairs.