It is believed that people can accumulate virtues by praying to deities such as Kannon. Thus, they want to pray to Kannon many times. This created some special days at a temple such as Sensoji Temple. Today (July 10th) is the most special day. If you visit Sensoji Temple and pray to Kannon then it deserves to pray to Kannon for 46,000 days.
I visited Sensoji Temple today. It was very crowded. However, most visitors do not know the meaning of today. They came to the temple because festival was held.
Many people bought a good-luck charm (omamori in Japanese) for averting thunder. In the Edo period, people feared thunder because it caused fire. One year, thunder happened. But, farmer houses where red corns were hanged were safe. Thus, red corns were sold in hope of averting thunder at Sensoji Temple. In the Meiji period, there was a bad harvest of red corns. Since then, omamori for averting thunder has been sold.