The Birth of Baha'u'llah commemorates the birth in 1817, at Tehran, of Mirza Husayn-Ali Nuri, known as Baha'u'llah ("the Glory of God"), the founder of the Baha'i Faith, whom Baha'is regard as the most recent in the succession of divine messengers that includes Abraham, Moses, Jesus, Muhammad, the Bab and others. It is the second of the Twin Birthdays, kept on the day after the Birth of the Bab; because the two were born on consecutive days by the Islamic lunar calendar, Baha'is celebrate them on two successive days set by a lunar reckoning, usually falling in October or November.
Baha'u'llah's life, from Persian nobleman to prisoner and exile carried across the Ottoman Empire to the prison-city of Acre, and his voluminous writings, are the foundation of the Baha'i teaching of the oneness of God, the oneness of religion, and the oneness of humanity. The day is one of the nine holy days on which work is suspended, observed with devotional gatherings, prayers and readings. As the birthday of their faith's founder, it is among the most significant and joyful of Baha'i anniversaries, and its pairing with the birth of the Bab links the messenger to the herald who announced him.