When did Leopold Vail Epstein change his name to Lee Eastman?

Lee Eastman came into this world as Leopold Vail Epstein on January 12, 1910. He was the son of Russian immigrants Louis Eastman and Stella Freyer. He graduated from Harvard Law School at a time in which that famed institution did not have many Jewish-Americans. Shortly after earning his Harvard law degree, Leopold Epstein changed his named to Lee Eastman. He married Louise Linder, the heiress to the Linder Department store chain. They had four children, including the future Mrs. Linda McCartney and John Eastman, an entertainment lawyer who would also figure prominently in Paul's Beatles and post-Beatles business dealings.

Linda McCartney's father's name wasn't always Lee Eastman, he was originally born Leopold Vail Epstein. In 1933 the society page of the New York Times ran an announcement that read:
"Mr. and Mrs. Max J. Lindner of this city have announced the engagement of their daughter, Miss Louise Dryfoos Lindner, to Leopold Vail Epstein, son of Mr. and Mrs. Louis Epstein of New York. Miss Lindner attended the Laurel Country Day School and graduated in 1933 from Smith College. Mr. Epstein, who is practicing in New York, studied at Harvard University and was graduated from law school there in 1933."
However, by 1939 it seems that Eastman was preferred and an announcement ran which read:
" A son was born to Mr. and Mrs. Leopold Vail Eastman of 12 East 88th Street on July 10 at Doctors Hospital."
Don't know when her dad changed his name to Lee.