I know in many Muslim countries, they take Friday off as their religious day, and in Israel it’s Saturday. So clearly, the day of rest doesn’t have to be Sunday, Sunday is just the day specified by Christianity.
So why would a country like China, whose government is actively anti-religion, or a country like Japan, which has never been colonized, choose to take Sundays off? There must have been some point in history when weekends were not a set thing.
Great question. They actually developed independently.
In Japan, the pre-Meiji period featured the Ichirokubi system. This was quite simple, the 1st, 6th, 11th, 16th, 21st, 26th of each month were rest days. This continued until 1876, when Japan decided to change the system as part of the Meiji Westernisation drive to follow the Western version of Sunday as a holiday. On average, the old system would have given two more rest days, so to appease unhappy workers, Saturday was designated as a half-day. Eventually, in line with the rest of the world, weekends became two days as well.
In China, the earliest records we have of official rest days come form the Huoguangzhuan written in c.50AD in the Han Dynasty. Then, the practice was called Xiumu or rest and wash, where officials were given 1 day every 5 days of work intended for both hygiene and recovery. By the Tang Dynasty this involved into the Shixun system, where officials had 2 days of rest for every 10 days of work. Both systems were intended to be flexible, and there were no fixed days. The concept of the weekend itself arrived from the West, and was first adopted by missionaries and missionary schools. Having Sunday as a rest day was so well received, the Qing Dynasty finally implemented it in all schools in Aug 1902. The Guangxu Emperor was a puppet of his mother, and the Empress eventually issued a decree that the Emperor be allowed to rest on Sundays as well, which in 1906 was extended to the rest of the court, and from there to the rest of the country.