[6] Baháʼu'lláh, the founder of the Baháʼí Faith, who claimed to be the one prophesied by the Báb, confirmed and adopted this calendar.
Around 1870, he instructed Nabíl-i-Aʻzam, the author of The Dawn-Breakers, to write an overview of the Badíʿ calendar.
[2][8] Baháʼu'lláh set Naw-Rúz to the day on which the sun passes into the constellation Aries.
Baháʼís interpret this formula as a specification of the vernal equinox, though where that should be determined was not defined.
[citation needed] On 10 July 2014 the Universal House of Justice announced provisions that will enable the common implementation of the Badíʿ calendar worldwide, beginning at sunset 20 March 2015,[10] coinciding with the completion of the ninth cycle of the calendar (see below).
[12] The Universal House of Justice selected Tehran, the birthplace of Baháʼu'lláh, as the location at which the time and date of the vernal equinox is to be determined according to astronomical tables from reliable sources.
Sociologist Eviatar Zerubavel notes that the nineteen-day cycle creates a distinctive rhythm which enhances group solidarity.
[22] Robin Mirshahi suggests a possible link with four realms described in Baháʼí cosmology.
[23] In the following table, the Gregorian date indicates the first full day of the month when Naw-Rúz coincides with 21 March.
These days are inserted between the 18th and 19th months, falling around the end of February in the Gregorian calendar.
The annual Nineteen Day Fast is held during the final month of ʻAláʼ.
The Metonic cycle represents an invented measure that approximately correlates solar and lunar markings of time and which appears in several calendar systems.