Old holidays die hard.
Throughout the Persian-speaking world—Iran, Afghanistan, Kurdistan—the Winter Solstice is a widely-celebrated, if secular, holiday. (For Zoroastrians, of course, it retains its religious character.) In Farsi, it's called Yalda, a word which may or may not be related to the Semitic root YLD, “to give birth.”
It's customary to stay up all night, to see the year's longest night through from beginning to end. People pass the long candle-lit hours, as one would expect, telling stories, singing songs, and eating. In Iran, the tradition is to serve 13 different fresh fruits—pomegranates, melons, cucumbers—one for each moon of the coming year.