Originally, "miso" was written as 三十, indicating the 30th day, though misoka sometimes fell on the 29th due to the varying lengths of the lunar month.

[1][2] As part of the Meiji Restoration, Japan switched to the Gregorian calendar in 1873, and ōmisoka was set as December 31, or New Year's Eve.

[2] Some of these include house cleaning, repaying debts, purification (such as driving out evil spirits and bad luck), and bathing so the final hours of the year could be spent relaxing.

[1] This custom has its roots in the ancient Japanese culture surrounding toshigamisama (歳神様) or toshitokusama (歳徳様), which revolved around the practice of showing reverence toward the gods of the current and upcoming years.

Throughout Japan, Shinto shrines prepare amazake to pass out to crowds that gather as midnight approaches.