This day is an official holiday in Iran, marking the end of Nowruz. Iranians annually celebrate the festive occasion after spending 12 days of Nowruz holidays with picnicking outdoors in nature.
Sizdah-Bedar ceremony is held with various methods and customs in different parts of Iran.
Different ceremonies based on each region’s culture are common on Sizdah-Bedar day, such as games, sports, local matches, wearing traditional clothes, playing music, local and group dances, eating lettuce with Sekanjebin (a traditional sweet and sour syrup), and cooking local foods, including different types of broth.
Source: Visitiran.ir