As per the Talmud, the month of Kislev marks the onset of the winter season in the Holy Land and is the third month of the "Season of the Rains."
Link: Winter
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).
Today is Rosh Chodesh ("Head of the Month") for the month of Kislev.
Special portions are added to the daily prayers: Hallel (Psalms 113-118) is recited -- in its "partial" form -- following the Shacharit morning prayer, and the Yaaleh V'yavo prayer is added to the Amidah and to Grace After Meals; the additional Musaf prayer is said (when Rosh Chodesh is Shabbat, special additions are made to the Shabbat Musaf). Tachnun (confession of sins) and similar prayers are omitted.
Many have the custom to mark Rosh Chodesh with a festive meal and reduced work activity. The latter custom is prevalent amongst women, who have a special affinity with Rosh Chodesh -- the month being the feminine aspect of the Jewish Calendar.
Links: The 29th Day; The Lunar Files
Far deeper than the wisdom to create is the wisdom to repair.
And so, G-d built failure into His world, so that He could give the human being His deepest wisdom: The wisdom of healing a shattered world and repairing our own selves.