FOUNDER’S DAY: American Ballet Theater opens its fall season at City Center on Wednesday with a gala that pays tribute to its very earliest days when one of its major assets was the creative presence of the great, but ailing, Russian choreographer Michel Fokine (1880-1942). The gala will include an excerpt from Fokine’s “Les Sylphides,” which in 1940 opened the company’s very first season. Later in this three-week season, the complete ballet will be revived, and Wednesday’s performance also includes the choreographer’s “Le Spectre de la Rose,” in which the role made famous by Vaslav Nijinsky will be taken by ABT’s latest wonder boy, Herman Cornejo. The program also celebrates the 20th anniversary season of principal dancer Alessandra Ferri, who will be seen with Angel Corella in the Jerome Robbins duet “Other Dances.” The entire season is packed with dance and dancers, and later features the world premiere of Trey McIntyre’s “Pretty Good Year” and the U.S. premiere of Christopher Wheeldon’s “VIII.” City Center, 55th Street between Sixth and Seventh Avenues; (212) 581-1212.