After sudden shutdowns and a scramble to teach classes online, Japan's educators are facing the prospect of another big coronavirus adjustment: starting school in September instead of April.

Although authorities are still weighing the change, which could happen next year, teachers and principals are baffled by the abrupt emergence of an idea that could dramatically alter how the country learns, lives and works.

September starts are a throwback to the Meiji Era (1868-1912). Calls to revert have been considered and shelved in the recent past.