Japan doesn't have just Labor Day on May 1st, but several national holidays around that date. Starting from 1985, the Japanese government simply created a block of consecutive holidays from the end of April to early May, lasting at least a week, and sometimes combined with two weekends, providing up to eleven days of vacation. This is commonly known as "Golden Week" — a term that originated from the Japanese cinema industry, because box office revenues would surge during this period of continuous holidays, resulting in very high attendance, hence the week being called the golden week.
The day after Kiyomi Liuli's father injured himself, the school started a long holiday. Kiyomi Koko also took her younger daughter on the earliest JR line to Sapporo, planning to stay there for a while, at least until her husband's injury healed, ensuring he wouldn't drink while injured.