during the civil war
no . the point of a president is that there is only one at a time. there never are two presidents at once because the constitution only allows one . unless you count the vice president that is the only way there could be two
George Washington was the second time, and John Adams.
The probability, over presidents of all organisations, through all of time, is 1.
Kennedy and Johnson
Two terms or ten years.
Yes, they can be elected to two terms but not to three.
Kennedy and Cleveland
Some Presidents served more than one term.
There were two events that 5 US presidents attended at the same time. The first one is the opening of the Ronald Reagan Presidential Library on November 4, 1991. This was also the first time in history that there were 5 presidents together at an event. The presidents were: Nixon, Ford, Carter, Reagan, and the senior Bush. The second time was at the funeral of Richard Nixon on April 27, 1994. The presidents there were: Ford, Carter, Reagan, the senior Bush, and Clinton.
George Clinton and Elbridge Jerry (both died in office)
Some presidents are elected to two four year terms and leave office at the end of their term in office. Some presidents are elected to one four year term and leave at the end. The other presidents died in office, except Richard Nixon who was forced to resign.