The Kitáb-i-Aqdas - The Most Holy Book
Index term: based on solar year, under Calendar, Bahá’í­
n27.
Let the days in excess of the months be placed before the month of fasting.
The Badí­' calendar is based on the solar year of 365 days, 5 hours, and 50 odd minutes. The year consists of 19 months of 19 days each (i.e. 361 days), with the addition of four extra days (five in a leap year). The Báb did not specifically define the place for the intercalary days in the new calendar. The Kitáb-i-Aqdas resolves this question by assigning the “excess” days a fixed position in the calendar immediately preceding the month of 'Alá', the period of fasting. For further details see the section on the Bahá’í­ calendar in The Bahá’í­ World, volume XVIII.
n138.
All Feasts have attained their consummation in the two Most Great Festivals, and in the two other Festivals that fall on the twin days
This passage establishes four great festivals of the Bahá’í­ <span class="highlight">year. The two designated by Bahá’u’lláh as “the two Most Great Festivals” are, first, the Festival of Ridván, which commemorates Bahá’u’lláh’s Declaration of His Prophetic Mission in the Garden of Ridván in Baghdád during twelve days in April/May 1863 and is referred to by Him as “the King of Festivals” and, second, the Báb’s Declaration, which occurred in May 1844 in Shí­ráz. The first, ninth and twelfth days of the Festival of Ridván are Holy Days (Q&A 1), as is the day of the Declaration of the Báb.
The "two other Festivals" are the anniversaries of the births of Bahá’u’lláh and the Báb. In the Muslim lunar calendar these fall on consecutive days, the birth of Bahá’u’lláh on the second day of the month of Muharram 1233 A.H. (12 November 1817), and the birth of the Báb on the first day of the same month 1235 A.H. (20 October 1819), respectively. They are thus referred to as the "Twin Birthdays" and Bahá’u’lláh states that these two days are accounted as one in the sight of God (Q&A 2). He states that, should they fall within the month of fasting, the command to fast shall not apply on those days (Q&A 36). Given that the Bahá’í­ calendar (see notes 26 and 147) is a solar calendar, it remains for the Universal House of Justice to determine whether the Twin Holy Birthdays are to be celebrated on a solar or lunar basis.
n147.
The number of months in a year, appointed in the Book of God, is nineteen.
The Bahá’í­ <span class="highlight">year, in accordance with the Badí­' calendar, consists of nineteen months of nineteen days each, with the addition of certain intercalary days (four in an ordinary year and five in a leap year) between the eighteenth and nineteenth months in order to adjust the calendar to the solar year. The Báb named the months after certain attributes of God. The Bahá’í­ New Year, Naw-Rúz, is astronomically fixed, coinciding with the March equinox (see note 26). For further details, including the names of the days of the week and the months, see the section on the Bahá’í­ calendar in The Bahá’í­ World, volume XVIII.