Upon mustering out of the Navy, he returned to his business career, but his illness forced him to retire in 1903 and seek to improve his health in Arizona and Colorado.

Scenes from the book, along with its 1932 predecessor God and My Father, and its 1937 sequel Life with Mother, published posthumously, were the basis for the 1939 play by Howard Lindsay and Russel Crouse, which became one of Broadway's longest-running non-musical hits.

According to James Moske, an archivist with the New York Public Library, who arranged and cataloged the library's Clarence Day Papers, a survey of Day's early short stories and magazine columns reveals "he was fascinated by the changing roles of men and women in American society as Victorian conceptions of marriage, family, and domestic order unraveled in the first decades of the twentieth century."

Day achieved lasting fame in literary circles for his comment "The world of books is the most remarkable creation of man.

[15] The American Library Association honored individuals for outstanding work in encouraging the love of books and reading with the Clarence Day Award from 1959-1980.

He rose to the rank of major in the Imperial Camel Corps, was wounded in battle in 1918 and received the Military Cross and Order of the Nile.

[18] Day died in New York City of pneumonia shortly after the publication of Life with Father, after it became a best-seller but before its success on Broadway.