'Ayyám-i-Há, or Intercalary Days, are the four days (five in a leap year)

During 'Ayyám-i-Há, Bahá’ís strive to show extra love, fellowship, and charity. 'Ayyám-i-Há is also a time when Bahá’ís give and receive gifts, particularly to children. As the Bahá’í calendar consists of the 19 months with 19 days each, the intercalary days provide an extra four days (or five in leap years) to complete the solar cycle. between the Bahá’í month of Mulk (February 7 – February 25) and the last month of the Bahá’í year, ‘Alá’ (March 2 – March 20), which is the month of fasting.

I entreat Thee, O my Lord, by these days and by all such as have during that period clung to the cord of Thy commandments, and laid hold on the handle of Thy precepts, to grant that unto every soul may be assigned a place within the precincts of Thy court, and a seat at the revelation of the splendors of the light of Thy countenance.

These, O my Lord, are Thy servants whom no corrupt inclination hath kept back from what Thou didst send down in Thy Book. They have bowed themselves before Thy Cause, and received Thy Book with such resolve as is born of Thee, and observed what Thou hadst prescribed unto them, and chosen to follow that which had been sent down by Thee. Thou seest, O my Lord, how they have recognized and confessed whatsoever Thou hast revealed in Thy Scriptures. Give them to drink, O my Lord, from the hands of Thy graciousness the waters of Thine eternity. Write down, then, for them the recompense ordained for him that hath immersed himself in the ocean of Thy presence, and attained unto the choice wine of Thy meeting.

I implore Thee, O Thou the King of kings and the Pitier of the downtrodden, to ordain for them the good of this world and of the world to come. Write down for them, moreover, what none of Thy creatures hath discovered, and number them with those who have circled round Thee, and who move about Thy throne in every world of Thy worlds. Thou, truly, art the Almighty, the All-Knowing, the All-Informed."

~Baha’u’llah]