Which US President served the shortest term in office?

William Henry Harrison, 9th President ,who died in office on April 4, 1841.served the shortest term of any president: March 4 - April 4, 1841. He served 30 days, 12 hours, and 30 minutes. He died of pneumonia.
William Henry Harrison only held office for 32 days. He died at the age of 68 from complications due to pneumonia.

William Henry Harrison who died after a month in office has this dubious distinction.