Something I never see being talked about in these sorts of threads is how Japan switched from the local lunisolar calendar to the Gregorian calendar. In the year 1872 (Meiji 5) the imperial government were paying their officials on a monthly basis, but their finances were in trouble, and the 6th month of the following year (Meiji 6) was a leap month which meant that they would have to budget an extra month's worth of pay for that year. Adopting the Gregorian calendar turned out to be a way out of this problem. As a "bonus", if they adopted it starting 1873 then the 12th month of the current year would only last two days and they could get away with skipping that month's pay completely.

The calendar reform was officially announced on the 9th day of the 11th month of Meiji 5, or 9 December 1872, to take effect 1 January 1873. This understandably caught people off guard, especially since official calendar makers had already started selling calendars for the new year a month earlier.