The night of Mehr’s birth, origin of Christmas

"Yalda" is a celebration with a record length of at least seven thousand years. This celebration is persisted like Nowruz Sizdah be Dar and Mehregan and etc. after defeat of the Persians from Macedonians, Mongols and Turks attacks and every year it is held in all Iranian houses.
The word "Yalda" is a Syriac word- Aramaic dialects in northern Mesopotamia means birth and procreation-. Because, this celebration is celebrating the birth and increasing Sun / Mehr / Mitra.
At least seven thousand years ago our ancestors reached the knowledge of the calendar and they found that the last night in December and early winter night is the longest night of the year. In a part of the Shahnameh of Ferdowsi, we read such a thing:
Spring and winter won’t come, unless promising be brought at the time of Ramesh
From these verses, it can be realized, other countries except Iran didn’t know about beginning of seasons, but the Persians at the time had acquired to this knowledge. Monthly and traditional festivities are the celebrations that are held based on the solar calendar.
We know that the Iranians have held their religious rituals with joy and lighting. The religious rituals that are held in loving family space and away from any aberration and corruption. This is the motivation that Iranian are awake in the longest night of the year –Yalda night- with their family especially the elders to watch the emergence of the sun and the light. Staying awake and keep homes light in this night is a symbol of help to light/sun in darkness and evil until the emergence of the sun and the arrival day.
Iranians were always famous for their qualities such as honesty, courage, and worship. In the Iranian thought, the evil spirit is the source of evil and darkness and lies. In the Iranian thought, lie has bogey form and it is identified as a demon.

In the Avesta Mehr Yasht, we read:

"Mehr looks on Iranian with thousands of eyes from the sky, so that they do not to lie."

In the Ordibehesht Yasht, we read:

"Lie must be ruined, lie must be overthrown, lie must be destroyed, and in the material world truth must overcome lie."
Or, for example, Darius in his inscriptions wanted God to protect Iran and keep it away from three things "lie, drought and enemy". Or in the inscription of Behistun, he stated lying as one of the major sins of rebels.
Mehr ritual also went to Europe during three fragmentation of Aryans and migration of some Aryans to Europe. In ancient Rome, Julian one of the Roman kings converted to this religion. The emperors like Commodus, Septum Soros, Caracalla, and famous Julian and also many Roman soldiers and officers were the followers of this religion and they built numerous synagogues and temples for Mitra at the edges of the Rhine, Danube and the Euphrates rivers. For many years, they celebrated Mehr birthday and Yalda night and they considered it as the beginning of the year. Even after expansion of the Christians religion (Christianity) in Europe, this night was a very superb night and became unique with the birth of Jesus Christ.
Varjavand day of Europeans means Sun + Day means the day of sun, or decorate a Cypress with two strands of silvery and golden ribbon by Iranians in the past, and many other symptoms show the influence of Mehr religion on Europe and the West and in fact, it links the origins of Christmas to the Iranian night of Yalda.

/J