From wikipedia:
Tenure and term limits
Franklin D. Roosevelt was elected to four terms before the adoption of the Twenty-second Amendment in 1951.
"The term of office for president and vice president is four years. George Washington, the first president, set an unofficial precedent of serving only two terms. Before Franklin D. Roosevelt, Ulysses S. Grant and Theodore Roosevelt each unsuccessfully sought a third term. In 1940, Franklin D. Roosevelt was elected to a third term after being "drafted" by his party. In 1941, the United States entered World War II, leading voters to elect Roosevelt to a fourth term in 1944. Roosevelt died on April 12, 1945, 82 days into his fourth term.
After the war, and in response to Roosevelt being elected to third and fourth terms, the Twenty-second Amendment was adopted. The amendment bars anyone from being elected president more than twice, or once if that person served more than half of another president's term. Harry S. Truman, president when this amendment was adopted, was exempted from its limitations and briefly sought a third (a second full) term before withdrawing from the 1952 election."
So the 28th Amendment only stipulates two terms. One president did serve non-consecutive terms (Grover Cleveland?) tho that was before the current rules anyway