On the 13th day of the month of Farvardin, Iranians celebrate a festival known as Sizdah Be-dar, also referred to as Nature Day.
It is a public holiday in Iran that falls on April 2 in the Gregorian calendar.
Sizdah Be-dar is an ancient Persian festival that dates back to the era of mythological king Jamshid, who is believed to have celebrated it together with his people.
It is an outdoor festival that celebrates family and friendship.
Ancient Iranians also believed that on this day, the demon of drought was defeated by the angel of rain.
They sacrificed sheep and cooked kebab to celebrate the demon's defeat.
The festival of Sizdah Be-dar also has its roots in Zoroastrianism.
Zoroastrians believe that the joyous celebration of this holiday helps cleanse all bad thoughts. In present-day Iran, Sizdah Be-dar is a say for celebrating people's friendship with nature.
Iranians spend it picnicking in parks and gardens.