Ayyám-I-Ha

The Persian phrase “Ayyam-i-Ha” – which simply means “the days of Ha” – describes the four or five intercalary days in the annual Baha’i calendar when Baha’is rejoice, do charitable work and prepare for the nineteen-day Baha’i fast that always follows Ayyam-i-Ha.

In the Arabic alphabet, the letter “Ha” has several spiritual meanings, and one of them symbolizes the essence of the Creator. The days of Ha, then, have a special significance in every Baha’i year, symbolizing the happiest and most celebratory qualities of the Supreme Being. That’s why, in most Baha’i communities around the world, you’ll find Baha’is having parties and celebrations during Intercalary Days.

The Intercalary Days occur because the Baha’i calendar has a unique system of nineteen months, each made up of nineteen days.

Sourced from https://bahaiteachings.org/what-are-the-bahai-intercalary-days