明けましておめでとうございます.
Japan marks the change of the lunar zodiac on the first day of the Gregorian (solar) calendar. For many years, I've wondered about how this astro-temporal mismatch came to be.
I finally looked into it by doing what all resourceful people do these days.
I asked ChatGPT to elucidate.
The answer is below, super-duper-heavily edited for clarity, brevity, vocabulary, grammar and style (turns out ChatGPT really needs an editor):
Japan used to celebrate new year based on the lunar calendar. However, Japan decided to switch to the Gregorian (solar) calendar in 1873 (during the Meiji period) to align with industrialising countries. The start of the year then became January 1 instead of the first day of the lunar year. Along with this change, the use of the lunar zodiac was shifted to the new solar-calendar convention.
Thus today marks the beginning of year of the dragon in Japan. The bunny rabbit still presides a little longer in other Asian countries.
The photo above is Oogway playing "Look, I'm a dragon!"—early-morning autumn light turning her claws dragons-breath orange.