Nature Day, known as ‘Sizdah Be-dar’ in Persian, is an Iranian public holiday celebrated on April 2 in normal years and April 1 in leap years. It marks the end of the Nowruz celebrations and occurs on the 13th day of ‘Farvardin,’ the first month of the Iranian calendar. This day is characterized by picnicking, where Iranians of all ages relax and enjoy outdoor activities in parks and the countryside. The holiday has its roots in Zoroastrianism and was originally a day to worship the god of rain, Teshtar. Over time, it has evolved into a cultural celebration, where participants believe that spending time outdoors helps to dispel bad luck associated with the number 13. Customs include releasing green plant shoots into flowing water, playing pranks known as the ‘Lie of the Thirteenth,’ and enjoying traditional foods like ‘Sekanjabin’ and ‘Ash-e Doogh.’