I was remiss in not posting this earlier today, but in my defense I forgot. Actually I guess that’s not really a defense.
The holiday known as یَلدا (Yaldā) marks the Winter Solstice, the shortest day of the year and the point at which the days begin to get longer again until summer. The word یلدا derives from the Arabic root ولد (W-L-D), which mean “birth,” and here it refers to the annual “birth” of the sun as its time in the sky begins to lengthen once more. The holiday has other names, like زایِش مِهر (Zayishmihr), which literally means “birth of the sun” (مهر is one of several alternatives for “sun” in Persian), شَبِ یَلدا (shab-i yaldā) or “night of birth,” and شَبِ چِله (shab-i chillah) or “night of forty” (the number 40 in Persian is چَهَل or chahal, but چله in one context refers to the first forty days of winter).
Yalda is a relic of Iran’s Zoroastrian past, when it was identified as the birthday of the angelic divinity Mithra, who was exalted just below the Zoroastrian god Ahura Mazda, and was identified with, though not identical to, the sun itself (مهر can also mean “Mithra,” making Zayishmihr “the birth of Mithra”). Ahura Mazda, Mithra, and the divine figure Apam Napat make up the “Ahuric Triad,” the worship of which was in fashion at some point in the development of Zoroastrianism, under the Achaemenids, though Ahura Mazda is set apart from the other two in Zoroastrian cosmology as the god, who is opposed by the evil force known as Ahriman. Any similarities that Mithra’s story might share with those of any other dieties you may hear about at this time of year is, of course, entirely coincidental, I’m sure. It is not an official holiday in Iran (the clerical leaders of Iran tend to frown on pre-Islamic holidays, and Yalda isn’t at the “don’t even think about touching this” level of Nowruz), but it is widely, if informally, observed nonetheless.
Chief among Yalda’s traditions is a large family dinner, including the traditional foods of the holiday: watermelon, pomegranate, nuts, and dried fruit. These foods are traditionally thought to have the power to protect the eater from the hassles and dangers of the summer months (insects and heat, mostly). People will frequently stay up all night or at least very late, possibly reading from the works of the great 14th century Iranian poet Hafez, telling stories, and dancing. Wine is frequently a part of the celebration as it is for so many Iranian festivals, in spite of the national ban on alcohol due to its prohibition in Islamic law (there is probably no disconnect between religious law and traditional culture in the world that is so great as Iran’s legal prohibition on wine).
So شَبِ یَلدا مُبارَک (shab-i yaldā mubārak, “Blessed Night of Yalda”) to you and yours!