The Intercalary Days
The intercalary days are a time of feasting, rejoicing, and charity for Baha'is.
Baha’u’llah, Founder of the Baha’i Faith, begins one of His prayers in the following way:
To Baha’is, the days named “Ayyam-i-Ha” mentioned in this prayer are the “Intercalary Days” established by Baha’u’llah and which appear in His Most Holy Book, the Kitab-i-Aqdas.
These Intercalary Days, or “Days of Ha,” occur between the eighteenth and nineteenth months of the Baha’i Calendar (February 26 to March 1 inclusive), and end one day before the Baha’i fast begins. There are four Intercalary Days in ordinary and five in leap years. These are days of preparation for the Fast; days of hospitality, charity, ministering to the poor and sick, the giving of presents, and so on.
In order to understand how the “Days of Ha” fit in the Baha’i calendar, it is necessary to understand this calendar.
It was the Bab, the precursor to Baha’u’llah, who introduced a new calendar which was later named the Badi' or Baha'i calendar. According to this calendar, a day is the period from sunset to sunset. The Bab ordained the month of 'Ala' (March) to be the month of fasting and decreed that the day of Naw-Ruz (New Year), which is on March 21st, should mark the termination of that period.
Naw-Ruz, therefore, is the first day of the Baha’i New Year. It coincides with the spring equinox in the northern hemisphere, which usually occurs on 21 March. Baha'u'llah explains that this occasion is to be celebrated on whatever day the sun passes into the constellation of Aries (i.e. the vernal equinox). The Naw-Ruz Festival could fall on 20, 21, or 22 March, depending on the time of the equinox.