Kamen Rider 35th Anniversary

The Kamen Rider 35th Anniversary was commemorated in 2006, which saw the broadcast of Kamen Rider Kabuto following the conclusion of Kamen Rider Hibiki.
 * 35th Masked Rider Anniversary File was attached to several episodes of Kabuto.
 * In-universe, the Masked Rider Project was said to have started on April 3rd of 1971, the premiere date of the original series.