The ceremony is called the inauguration.
inauguration
inauguration
inauguration
The ceremony begins at 11:30 A.M. on January 20th. There are a number of program items leading up to President Obama's oath of office, including the swearing in of Vice President Biden. So President Obama's swearing in will occur at approximately noon.
I would guess it is to avoid the problem of divided loyalty.
The loyalty boards were originally created and initiated by President Truman.
John Adams told the Second Continental Congress that the 13 Colonies did not owe loyalty to the British King.
by an order of president truman
unswerving loyalty and support
federal employee loyalty program
Loyalty
yes