Solar Calendar Adoption Day

What Is Solar Calendar Adoption Day?

Every November 9th is "Solar Calendar Adoption Day" (太陽暦採用記念日, Taiyōreki Saiyo Kinenbi) in Japan. On the 9th day of the 11th month of Meiji 5 (1872) by the old calendar, the Meiji government officially issued the Daijōkan Proclamation (太政官布告) announcing that Japan would adopt the Gregorian solar calendar — replacing the traditional lunisolar calendar: the day after the 2nd day of the 12th month of Meiji 5 became January 1, 1873 — in other words, what would have been the 3rd day of the 12th month became New Year's Day. The decision, announced on this day, was one of the most sweeping administrative changes of the Meiji modernization period.

Why Japan Changed Calendars

The Meiji government's decision to adopt the Gregorian calendar reflected the pragmatic necessity of aligning Japan's time-keeping with international standards as Japan integrated into the global commercial and diplomatic order. The traditional lunisolar calendar — with its months based on lunar cycles and periodic intercalary months added to keep the calendar aligned with the solar year — was incompatible with the fixed-date scheduling of international shipping, trade, and diplomacy. Additionally, the switch was announced with very short notice (just three weeks before the calendar change took effect), and it is often said that finances played a part: because the 12th month of Meiji 5 lasted only two days, the government could avoid paying a full month's salary for it, and it also avoided the extra intercalary month that the old calendar would have added in 1873.

Cultural Adaptation to the New Calendar

The transition to the solar calendar required the renegotiation of Japan's entire cycle of traditional festivals, agricultural practices, and ceremonial occasions. Many traditional events simply shifted to the same date in the new calendar — which was roughly a month earlier in the solar year — creating what some Japanese called a "one month out of step" quality to traditional events celebrated on solar calendar dates. Others retained the lunar timing: the "old New Year" (旧正月, kyū shōgatsu) and certain regional festivals still follow the lunar calendar.

Dual Calendar in Japanese Life

The legacy of the 1872 calendar switch is visible in contemporary Japan's complex relationship with time. Official and business contexts use the Gregorian calendar alongside Japan's imperial era dating system (currently Reiwa). Traditional festivals, Buddhist ceremonies, and some agricultural practices still reference the lunar calendar. Japan's relationship with calendrical time reflects its broader navigation of tradition and modernity.

Fun Facts

• Rokuyo survival: The traditional six-day auspiciousness cycle (六曜, rokuyo) — which designates days as fortunate, unfortunate, or neutral for various activities — continues to be printed on most Japanese calendars and consulted for wedding dates, business launches, and funerals, surviving 150 years of solar calendar use.
• Financial motivation: The extraordinarily short notice of the 1872 calendar switch (announced November 9, effective January 1 of the new calendar — just three weeks away) has often been attributed in part to the Meiji government's desire to save money — the two-day 12th month and the avoided intercalary month of 1873 meant fewer monthly salaries to pay.