Was 'acting president' for 8 hours in 1985
The official timeline for the George H.W. Bush presidency was from January 1989 until January 1993. However, a few years earlier Bush served as president for a grand total of 8 hours.
In 1985, while President Ronald Reagan underwent surgery, then Vice President Bush served as “acting president” for 8 hours. This marked the first time that the 25th Amendment, which was ratified in 1967, went into effect.
According to the Amendment, “In case of the removal of the President from office, or of his death, resignation, or inability to discharge the powers and duties of the said office, the same shall devolve on the Vice President, and the Congress may by law provide for the case of removal, death, resignation or inability, both of the President and Vice President, declaring what officer shall then act as President, and such officer shall act accordingly, until the disability be removed, or a President shall be elected.”