The network's programming season runs from February until the following March of each year when a retrospective of Oscar-winning and Oscar-nominated movies is shown, called 31 Days of Oscar. As a result of its devoted format to classic feature films, viewers that are interested in tracing the career development of actresses such as Barbara Stanwyck or Greta Garbo or actors like Cary Grant or Humphrey Bogart have the unique opportunity to see most of the films that were made during their careers, from beginning to end. Turner Classic Movies presents many of its features in their original aspect ratio (widescreen or full screen) whenever possible – widescreen films broadcast on TCM are letterboxed on the network's standard definition feed. TCM also regularly presents widescreen presentations of films not available in the format on any home video release.

Answer this question, if possible (if impossible, reply "unanswerable"): What retrospective of the Oscars is shown yearly on letterbox?
unanswerable