William E. Day, 69, a former commissioner and retired senior trial judge on the U.S. Court of Claims, died of cancer Wedneday at his home in New Smyrna Beach, Fla.

Judge Day, who was born in Washington, graduated from Eastern High School. From 1931 to 1937, he was a pressman at the Government Printing Office. During those years, he earned a bachelor's degree and two master's degrees in law at National University. One of his master's degrees was in patent law.

From 1937 to 1940, he taught at the Carnegie Institute of technology in Pittsburgh. He then returned to Washington and joined the Justice Department as a lawyer in the antitrust division.

Following World War II service in the Coast Guard, in which he became a commander, Judge Day went back to Justice.

In 1949, he was named a commissioner, or judge, of the Court of Claims. He held that post until 1973, when he took senior trial judge status. In 1974, he retired and moved from his home in Arlington to New Smyrna Beach.

In Florida, Judge Day was an arbitrator in the Construction Industry of the Southern Region. He retired from that work a year ago for reasons of health.

His wife, Mary Redmond Day, died in 1980.

Survivors include two sisters, Mary N. Parlon of Rockville and Anna Day Clayton of Rossmoor Leisure World in Silver Spring.