A Japanese shrine has recorded one lake's ice for 583 years, as a divination

At the Japanese shrine of 八剱神社, the freezing ice of Lake Suwa has been recorded for 583 years, serving as a form of divination. The process involves observing a ridge that forms across the lake, believed to be the path 八剱神神 crosses to reach another deity. This observation began in 1443 and continues to be logged each February by the Japan Meteorological Agency.

The longest uninterrupted period of ice has been 583 years, surpassing any other recorded absence. The ice record is maintained by the shrine despite a brief interruption during the Meiji government's decree in 1871. The record is maintained by counting the number of times the lake has frozen over, with 80 occurrences since 1443.

The divination ceremony takes place when three ridges are observed, signifying the crossing of deities from the north and east shores to the south shore. The ceremony is considered an intangible folk cultural property of the region and is held annually for the purpose of predicting the year's harvest, weather, and overall fortune.