Question: When was Kathryn Grayson of the 1946 American musical comedy, Ziegfeld Follies, under contract to Metro-Goldwyn-Mayer?

Context paragraphs:
A Parisian Model: A Parisian Model is a 1906 Edwardian musical comedy with music by Max Hoffman, Sr. to a book and lyrics by Harry B. Smith.  The story concerns a dressmaker's model who comes into a fortune.  It opened on Broadway in 1906, ran with success and toured.  It was produced by Frank McKee and Florenz Ziegfeld Jr., and starred Anna Held, Ziegfeld's common law wife.  Soon after the success of this piece, Ziegfeld would launch his famous series of "Ziegfeld Follies" revues.

Dick Williams (singer): Dick Williams (born June 7, 1926) is an American singer and actor.  He is the older brother of Andy Williams and had started out like Andy in The Williams Brothers.  Williams was born in Wall Lake, Iowa, the son of Jay Emerson and Florence (née Finley) Williams.  While living in Cheviot, Ohio, Williams attended Western Hills High School in Cincinnati, Ohio.  He finished high school at University High School, in West Los Angeles, because of his family's move to California.  Williams had brothers: Bob, Don, and Andy.  One of his first performance was in a children's choir at the local Presbyterian church.  He and his brothers formed the Williams Brothers quartet in late 1938, and they performed on radio in the Midwest, first at WHO, in Des Moines, Iowa, In July 1940 the family the family moved to Chicago and received a job at WLS, in Chicago, and WLW, in Cincinnati.  Moving to Los Angeles in 1943, the Williams Brothers sang with Bing Crosby on the hit record "Swinging on a Star" (1944).  They appeared in four musical films: "Janie" (1944), "Kansas City Kitty" (1944), "Something in the Wind" (1947) and "Ladies' Man" (1947). The Williams Brothers were signed by Metro-Goldwyn-Mayer to appear in "Anchors Aweigh" and "Ziegfeld Follies" (1945) but, before they went before the cameras, the oldest brother, Bob, was drafted into military service and the group's contract was canceled.  Kay Thompson, a former radio star who was now head of the vocal department at MGM, had a nose for talent and hired the remaining three Williams brothers to sing in her large choir on many soundtracks for MGM films, including "The Harvey Girls" (1946).  When Bob completed his military service, Kay hired all four brothers to sing on the soundtrack to "Good News" (1947).

Ziegfeld Follies (film): Ziegfeld Follies is a 1946 American musical comedy film released by Metro-Goldwyn-Mayer and directed by Lemuel Ayers, Roy Del Ruth, Robert Lewis, Vincente Minnelli, Merrill Pye, George Sidney and Charles Walters.  It stars many of MGM leading talents, including Fred Astaire, Lucille Ball, Lucille Bremer, Fanny Brice (the only member of the ensemble who was a star of the original Follies), Judy Garland, Kathryn Grayson, Lena Horne, Gene Kelly, James Melton, Victor Moore, William Powell, Red Skelton, and Esther Williams.

Ziegfeld Follies of 1936: The Ziegfeld Follies of 1936 is a musical revue with lyrics by Ira Gershwin, music by Vernon Duke and sketches by Gershwin and David Freedman.  The Ziegfeld Follies were a series of revues presented from 1907 through 1931, 1934, 1936, 1943, and 1957.

Glorifying the American Girl: Glorifying the American Girl is a 1929 American Pre-Code, musical comedy film produced by Florenz Ziegfeld that highlights Ziegfeld Follies performers.  The last third of the film (which was filmed in early Technicolor) is basically a Follies production, with cameo appearances by Rudy Vallee, Helen Morgan, and Eddie Cantor.

The Fabulous Palm Springs Follies: The Fabulous Palm Springs Follies was a Ziegfeld Follies style dance and musical review show that played at the historic Plaza Theatre in Palm Springs, California, United States, seasonally from November to mid-May.  The Follies was founded in 1990 by Riff Markowitz and Mary Jardin.  Impresario Markowitz also served as the show's managing director and emcee.  The show was often credited with helping to revitalize and maintain the downtown area by bringing in patrons from around the globe.  The Follies was unique in that it only featured performers 55 and older and holds Guinness World Records for this claim to fame.  It was the subject of a short documentary titled "" which was nominated at the 70th Academy Awards for Best Short Subject Documentary.  A segment that aired on Seattle television station KOMO-TV that featured the Follies received an Emmy in 1997.  The shows attracted approximately 170,000 attendees yearly.  On June 5, 2013, co-founders Markowitz and Jardin announced they would close the Follies on May 18, 2014.

Ziegfeld Follies: The Ziegfeld Follies was a series of elaborate theatrical revue productions on Broadway in New York City from 1907 through 1931, with renewals in 1934 and 1936.  They became a radio program in 1932 and 1936 as "The Ziegfeld Follies of the Air".

George White's Scandals: George White's Scandals were a long-running string of Broadway revues produced by George White that ran from 1919–1939, modeled after the "Ziegfeld Follies".  The "Scandals" launched the careers of many entertainers, including W.C. Fields, the Three Stooges, Ray Bolger, Helen Morgan, Ethel Merman, Ann Miller, Bert Lahr and Rudy Vallée.  Louise Brooks, Alice White, and Eleanor Powell got their show business start as lavishly dressed (or underdressed) chorus girls strutting to the "Scandal Walk."  Much of George Gershwin's early work appeared in the 1920–24 editions of "Scandals."  The Black Bottom, danced by "Ziegfeld Follies" star Ann Pennington and Tom Patricola, touched off a national dance craze.

Florenz Ziegfeld Jr.: Florenz Edward Ziegfeld Jr. (March 21, 1867 – July 22, 1932), popularly known as Flo Ziegfeld, was an American Broadway impresario, notable for his series of theatrical revues, the "Ziegfeld Follies" (1907–1931), inspired by the "Folies Bergère" of Paris.  He also produced the musical "Show Boat".  He was known as the "glorifier of the American girl".  Ziegfeld is a member of the American Theater Hall of Fame.

Kathryn Grayson: Kathryn Grayson (February 9, 1922 – February 17, 2010) was an American actress and coloratura soprano.  From the age of twelve, Grayson trained as an opera singer.  She was under contract to Metro-Goldwyn-Mayer by the early 1940s, soon establishing a career principally through her work in musicals.  After several supporting roles, she was a lead performer in such films as "Thousands Cheer" (1943), "Anchors Aweigh" (1945) with Frank Sinatra and Gene Kelly, and "Show Boat" (1951) and "Kiss Me Kate" (1953), both with Howard Keel.

Supporting paragraphs: Ziegfeld Follies (film) Kathryn Grayson
Answer: by the early 1940s