The birthdays of the Báb, born 20 October 1819, and of Bahá'u'lláh, born 12 November 1817, fall on consecutive days in the Islamic lunar calendar, and Bahá'u'lláh referred to them as twin festivals accounted as one. Until 2014 they were observed in the West on fixed Gregorian dates and in the Middle East on the lunar ones, which meant the community kept two different calendars. In 2014 the Universal House of Justice announced that from the following year the whole Bahá'í world would observe them on the first and second days following the occurrence of the eighth new moon after Naw-Rúz, calculated astronomically using tables based on Tehran. The effect is that the dates move each year within a range in October and November, which is administratively inconvenient and was accepted in order to restore a unified calendar and the calculation the Báb had specified. The same 2014 decision fixed Naw-Rúz astronomically as well.