1 to 3 months. Documentary is a technical person who is responsible for the compilation, collection, arrangement and file management of engineering project data. It takes 1 to 3 months from basic to semi-proficiency, but proficiency takes at least 1 to 2 years. The librarians need to pass the post qualification examination organized by the relevant state departments and obtain the corresponding certificates before they can take up the relevant positions. Some employers don't have independent librarians.