The Festivals of the Twin Birthdays or the Twin Holy Birthdays refers to two successive holy days in the Bahá’í calendar that celebrate the births of two central figures of the Bahá’í Faith. The two holy days are the birth of the Báb on the first day of Muharram in the Islamic calendar (20 October 1819) and the birth of Bahá’u’lláh on the second day of Muharram (two years prior, on 12 November 1817).[1][2][3]

They are observed on the first and the second day following the occurrence of the eighth new moon after Naw-Rúz, as determined in advance by astronomical tables using Tehran as the point of reference.[4] This results in the observance of the Twin Birthdays moving, year to year, within the months of Mashíyyat, ‘Ilm, and Qudrat of the Bahá’í calendar, or from mid-October to mid-November in to the Gregorian calendar.[5]

Prior to 2015 and a decision by the Universal House of Justice, these two holy days had been observed on the first and second days of Muharram in the Islamic lunar calendar in the Middle East, while other countries observed them according to the Gregorian calendar on October 20 (for the birth of the Báb) and November 12 (for the birth of Bahá’u’lláh).[2]

In 174 B.E. (2017) and 176 B.E. (2019) the bicentennial anniversaries of the Birth of Bahá’u’lláh and the Birth of the Báb will be celebrated.[5]

Year Dates (Badí’ Calendar) Dates (Gregorian Calendar) Bicentennials
172 B.E. Qudrat 10, 11 Nov 12/13, 13/14 (2015)
173 B.E. `Ilm 18, 19 Oct 31/Nov 1, Nov 1/2 (2016)
174 B.E. `Ilm 7, 8 Oct 20/21, 21/22 (2017) Bicentennial of the Birth of Bahá’u’lláh (From sunset on Friday October 20 to sunset on Sunday October 22)
175 B.E. Qudrat 6, 7 Nov 8/9, 9/10 (2018)
176 B.E. `Ilm 14, 15 Oct 28/29, 29/30 (2019) Bicentennial of the Birth of the Báb (From sunset on Monday October 28 to sunset on Wednesday October 30)
177 B.E. `Ilm 4, 5 Oct 17/18, 18/19 (2020)
178 B.E. Qudrat 4, 5 Nov 5/6, 6/7 (2021)


The notion of “twin Manifestations of God” is a concept fundamental to Bahá’í belief, describing the relationship between the Báb and Bahá’u’lláh. Both are considered Manifestations of God in their own right, having each founded separate religions (Bábism and the Bahá’í Faith) and revealed their own holy scriptures. To Bahá’ís, however, the missions of the Báb and Bahá’u’lláh are inextricably linked: The Báb’s mission was to prepare the way for the coming of Him whom God shall make manifest, who eventually appeared in the person of Bahá’u’lláh. For this reason, both the Báb and Bahá’u’lláh are revered as central figures of the Bahá’í Faith.[6] A parallel is made between Bahá’u’lláh and the Báb as between Jesus and John the Baptist.[7]

In the Kitáb-i-Aqdas, Bahá’u’lláh wrote that his birthday and that of Báb “are accounted as one in the sight of God”.[8]

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