Shabe Yaldā (Persian: یلدا) or Shabe Chelle (Persian: شب چله) is an Iranian festival originally celebrated on the Northern Hemisphere's longest night of the year, that is, on the eve of the Winter Solstice.

Following the Iranian calendar reform of 1925, which pegged some seasonal events to specific days of the calendar, Yalda came to be celebrated on the night before and including the 1st day of the 10th month (Dey). Subject to seasonal drift, this day may sometimes fall a day before or a day after the actual Winter Solstice.
 

History and development

The word Yalda derives from a Syriac term signifying "birth." A Winter Solstice festival - Shab-e Chelle - had already been celebrated throughout the Iranian world even prior to the introduction of the word Yalda during the early Sassanid Era. Like all other festivals tied to the solar calendar, Shabe Chelle has its roots in the close contacts between Chaldea/Babylonia and Iran during the late Achaemenid period.


The process by which the term Yalda entered the Persian language is not conclusively established, but is probably attributable to Syriac Christians who received protection from the Sassanid monarchs. While these Christians that brought Yalda to Iran presumably associated the festival with the birth of Christ, the proximity of December 25th to the day of the Winter Solstice (December 21st or 22nd) eventually led to the two festivals being conflated and celebrated as one. Nothwithstanding that, as in Iran also, evergreen trees everywhere symbolize the continuity of nature, Yule has its origins in Saxon/Norse culture and was originally a lunar calendar event.

Yalda Today
 

Following the fall of the Sassanid Empire and the subsequent rise of Islam, the religious significance of the event was lost, and like all the other Zoroastrian festivals Yalda became merely a social occasion when family and close friends would get together. Nonetheless, the obligatory serving of fresh fruit during mid-winter is reminiscent of the ancient customs of invoking the divinities to request protection of the winter crop.

The tradition of family gathering survives today in full force. Iranian radio and television continue to have special programming for the night of Yalda.

As a novelty, watermelons may appear at the Korsi. The Korsi is traditional furniture similar to a very short table, around which the family sit on the ground. On it, a blanket made of wool filling is thrown, people leave their legs under the blanket. Inside the korsi, heat is generated by means of coal, electricity or gas heaters.
 

Source: http://en.wikipedia.org/wiki/Yalda