Rebbe's Recovery (1977)

For the first time since suffering a major heart attack five weeks earlier, on the eve of Shemini Atzeret, the Rebbe left his office in 770 Eastern Parkway and returned to his home, signaling his recovery. Chassidim all over rejoiced at the good news.

From that day on, the Rebbe redoubled his efforts on behalf of the Jewish nation and all of humanity, and for the dissemination of Torah and chassidism. From then on, the first of Kislev is celebrated as a day of thanksgiving and rejoicing.

Link: Illness and Challenge (from the timeline "biography of ideas" in Therebbe.org).