Earliest date for Winter solstice's eve (Northern Hemisphere), and its related observances: Yaldā (Iran)

Yaldā Night or Chelle Night is an ancient festival in Iran, Kurdistan, Azerbaijan, Uzbekistan, Afghanistan, Tajikistan, Turkmenistan that is celebrated on the winter solstice. This corresponds to the night of December 20/21 (±1) in the Gregorian calendar, and to the night between the last day of the ninth month (Azar) and the first day of the tenth month (Dey) of the Iranian solar calendar.The longest and darkest night of the year is a time when friends and family gather together to eat, drink and read poetry and Shahnameh until well after midnight. Fruits and nuts are eaten and pomegranates and watermelons are particularly significant. The red colour in these fruits symbolizes the crimson hues of dawn and the glow of life. The poems of Divan-e Hafez, which can be found in the bookcases of most Iranian families, are read or recited on various occasions such as this festival and Nowruz. Shab-e Yalda was officially added to UNESCO Intangible Cultural Heritage Lists in December 2022.

Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the northeast, Afghanistan to the east, Pakistan to the southeast, and the Gulf of Oman and the Persian Gulf to the south. Iran ranks 17th globally in both geographic size and population and is the sixth-largest country in Asia. Iran is divided into five regions with 31 provinces. Tehran is the nation's capital, largest city, and financial center.