In the domain duties era, that’s the day Kaga Domain presents an ice to Tokugawa Bakufu goverment.

According to the documents, those ices were lapped with bamboo leaves and carried all the way of 120 Li(about 480 km) to Edo(Tokyo) with taking 4 days long.

Himuro means natural refrigerator to keep snow.

They used to save snow there in winter and open it up on July 1 st (June 1 st in old calendar).