Structure

The Bahá'í (or Badī') calendar begins its years on the day of the vernal equinox. Theoretically, if the actual time of the equinox occurs after sunset, then the year should begin a day later [2]. Current practice in the West, however, is to begin on March 21 of the Gregorian calendar, regardless. The theoretical, astronomical version of the Bahá'í calendar is described in Section 15.3. The calendar is based on the 19-year cycle 1844–1863 of the Bāb, the martyred forerunner of Baha'u'llāh and co-founder of the Bahá'í faith.

As in the Islamic calendar, days are from sunset to sunset. Unlike the Islamic calendar, years are solar; they are composed of 19 months of 19 days each with an additional period of 4 or 5 days after the eighteenth month. Leap years in the West follow the same pattern as in the Gregorian calendar.