30 Azar, the night of the winter solstice (about 20 December)
Shab-e Yalda is the longest night of the year. From the next morning the days grow longer, so the night is kept as a celebration of light returning.
Family and friends stay up together, usually at the home of the eldest, with pomegranates, watermelon, nuts and dried fruit on the table.
The heart of the night is the Divan. Each person makes a wish in turn, the eldest opens the book, and the ghazal is read aloud as that person's fal.