'Yalda' is a Syriac word meaning birth and according to Mithraism, a faith that initially originated from Persia and later spread out throughout the ancient civilized world, the first day of winter which falls on December 21 this year, was celebrated as the birthday of Mithra, the angel of light.

Ancient Iranians believed that two groups of angels -- good and bad -- were in constant fight on the earth with each other and that on the dawn of the first day of the month of 'Dey', beginning December 21, and with the victory of the rising sun as the symbol of 'Ahuramazda', the Zoroastrian god, over the evil of darkness the fight would come to an end.

People had developed the idea that the longest night of the year, when the evil of darkness found an opportunity to stay longer, was an inauspicious occasion and, therefore, they would gather together and stay awake the whole night by holding celebrations and lighting fire in order to leave behind the ominous night.

They would try to keep the fire lit all through the night and the person in charge of the task was called 'Atropat' or the 'guardian of fire' who used to have a religious rank in ancient Persia.

Ancient Iranians believed that the beginning of the year marked with the re-emergence or rebirth of the sun which coincided with the first day of the month of 'Dey' when sun was salvaged from the claws of the devil of darkness and gradually spread its domination over the world.

However, apart from its religious and traditional characteristics, 'Yalda' has long been observed in the Iranian culture as the longest night of the year.

On this night, all members of the family stay together, narrate old stories, play traditional games and eat dried fruits and candies. The fruits that are specially served at this night are sweet melon, water melon, grapes and pomegranates.

Fruits are symbol of spring and a summer loaded with agricultural bounties.

Another tradition that is observed on the night of Yalda is reading poems of the highly revered Iranian poet 'Hafez'.

They read and interpret the poem appearing on the page after reciting some holy words and opening a page of his Divan.