The Bahá'í calendar is a solar calendar organised as a hierarchy of cycles, each of length 19, commemorating the 19 year period between the 1844 proclamation of the Báb in Shiraz and the revelation by Bahá'u'lláh in 1863. Days are named in a cycle of 19 names. Nineteen of these cycles of 19 days, usually called "months" even though they have nothing whatsoever to do with the Moon, make up a year, with a period between the 18th and 19th months referred to as Ayyám-i-Há not considered part of any month; this period is four days in normal years and five days in leap years. The rule for leap years is identical to that of the Gregorian calendar, so the Bahá'í calendar shares its accuracy and remains synchronised. The same cycle of 19 names is used for days and months.

The year begins at the equinox, March 21, the Feast of Naw-Rúz; days begin at sunset. Years have their own cycle of 19 names, called the Váhid. Successive cycles of 19 years are numbered, with cycle 1 commencing on March 21, 1844, the year in which the Báb announced his prophecy. Cycles, in turn, are assembled into Kull-I-Shay super-cycles of 361 (19˛) years. The first Kull-I-Shay will not end until Gregorian calendar year 2205. A week of seven days is superimposed on the calendar, with the week considered to begin on Saturday. Confusingly, three of the names of weekdays are identical to names in the 19 name cycles for days and months.

Adapted from Formilab's Calendar Converter.