Generations (Howe and Strauss) and the age of the generations when their first member became President:
Awakening (1701-1724) NEVER
Liberty (1725-1742) 65 -- Washington, 1789
Republican (1743-1766) 58 -- Jefferson, 1801
Compromise (1767-1791) 58 -- J Q Adams, 1825
Transcendental (1792-1821) 62 -- Fillmore, 1850
Gilded (1822-1842) 47 -- Grant, 1867
Progressive (1843-1859) 54 -- McKinley, 1897
Missionary (1860-1882) 61 -- Harding, 1921
Lost (1883-1900) 62 -- Truman, 1945
GI (1901-1924) 60 -- Kennedy, 1961
Silent (1925-1942) -- probably never, 90 or 91 if something were to happen to Barack Obama
Boom (1943-1960) 50 -- Clinton, 1993
X (1961-1981) 48 -- Obama, 2009
No member of the Millennial Generation will be eligible to be President or Vice-President until 2017... and that would be someone born in early-to-middle January 1982.
Minimum 47 in history, maximum 65 for the generation (ignoring the Awakening Generation of Benjamin Franklin and almost certainly the Silent Generation)
1982 + 47 = 2029
1982 + 65 = 2047
...wins the Presidency in 2028, minimum; 2044 maximum.
So what do you call Jimmy Carter then? Born 1924, President in 1977.