Meiji era

Keiō 4, ninth month, eighth day

An imperial rescript changed the Japanese era name from Keiō to Meiji on the eighth day of the ninth lunisolar month, corresponding to 23 October 1868 in the Gregorian calendar.

It made the existing fourth year of Keiō the first year of Meiji, applying the new designation retroactively to the year already under way. Japan did not adopt the Gregorian calendar for domestic civil dating until 1873.

One emperor, one era

The same measure established issei ichigen, the rule that one era name would be used for one emperor's reign. Era changes would from then on follow imperial succession rather than recur within a reign.

Scholarly research identifies court scholars as having chosen "Meiji" from classical Chinese sources. The era name later became the emperor's posthumous imperial name.

What the rescript did not do

This was an era-name proclamation — not the January restoration of imperial government, not the abolition of the domains, and not the end of the Boshin War.

"Meiji" was also not adopted when Mutsuhito ascended the throne in 1867; Keiō continued until this document.

Saying the Edo period ended that day is conventional periodisation rather than a clause in the rescript. The period's end has several defensible markers, including Yoshinobu's 1867 return of power and the January 1868 abolition of the shogunate.