Sizdah Bedar is the Iranian festival of nature and is celebrated on the 13th day of the Iranian New Year, the occasion has deep roots in the Iranian history. The festivities include picnicking outdoors, in the parks or the countryside.
Although picnicking outdoors is the main event there are other purposes for the celebrations such as appreciating nature, cleaning the mind from evil thoughts and spending the day outdoors to stay away from the unluckiness of the number thirteen.