“the Days of Há”

Known as the Ayyam-i-Há (the Days of Há), the Intercalary Days have the distinction of being associated with "the letter Há". The abjad numerical value of this Arabic letter is five, which corresponds to the potential number of intercalary days. The letter "Há" has been given several spiritual meanings in the Holy Writings, among which is as a symbol of the Essence of God.

Bahá'u'lláh enjoined upon His followers to devote these days to feasting, rejoicing and charity. In a letter written on Shoghi Effendi's behalf it is explained that "the intercalary days are specially set aside for hospitality, the giving of gifts, etc.". 

(The “Notes” section of the Kitab-i-Aqdas containing annotations, prepared by the  committees commissioned by the Universal House of Justice)