* Early Attempts (1920s-1930s): The earliest attempts at widescreen were experimental and mostly limited to special events or short films. These included systems like "Cinerama" (1952) and "Todd-AO" (1955), which used multiple projectors to create a panoramic image.
* Widescreen Becomes More Common (1950s-1960s): The advent of CinemaScope in 1953 (and other similar formats like VistaVision and MGM Camera 65) helped popularize widescreen by offering a more affordable and convenient way to achieve the wider aspect ratio.
* The 1960s and Beyond: By the 1960s, most new movie theaters were built with widescreen projection capabilities. The widespread adoption of the 1.85:1 aspect ratio solidified widescreen as the standard for filmmaking.
Therefore, there's no single "start date" for widescreen in movie theaters. It was a process of gradual adoption, with significant developments in the 1950s leading to its widespread use by the 1960s.