ATLANTA – Former President Jimmy Carter marks his 96th birthday Thursday, the latest milestone for the longest lived of the 44 men to hold the highest American office.Carter planned to celebrate at his home in Plains, Georgia, with his wife of 74 years, Rosalynn Carter, according to a spokeswoman for the Carter Center in Atlanta.The 39th president, in office from 1977-81, has largely receded from public view amid the coronavirus pandemic and his own health challenges due to a series of falls in 2019.