The Bahá'i calendar is a solar calendar with regular years 365 days long and leap years 366 days long. Years are composed of 19 months of 19 days each, plus an extra period of either 4 or 5 days. Years in the Bahá'i calendar begin at the vernal equinox (usually March 21 in the Gregorian calendar). Days are considered to begin at sunset on the previous solar day.

Also existent in the Baha'i calendar system is a 19-year cycle called Vahid and a 361-year (19x19) supercycle called Kull i-Shay (literally, All Things.) The 9th Vahid in the 1st Kull i-Shay started in 1996. The 2nd Kull i-Shay won't begin until 2205.

Years in the Bahá'i calendar are counted from 21 March 1844 CE, the beginning of the Bahá'i Era (abbreviated BE)

See also calendars, Bahá'i Faith