The Day of the Covenant (November 26) had special significance for Bahá’ís everywhere. It was the festival which commemorated Bahá’u’lláh’s appointment of his eldest son ‘Abdu’l-Baha, as the Centre of his Covenant.
Bahá’ís observe 11 holy days each year which are commemorated with community gatherings for prayer, reflection, and fellowship. The Day of the Covenant was such a day. Learn more here: http://info.bahai.org/covenant-of-bahaullah.html