Question: Given a reference text about the history of the workweek, what social forces precipitated the creation of a five-day workweek in the United States and when?
Evidence: A continuous seven day cycle that runs throughout history, paying no attention whatsoever to the phases of the moon and having a fixed day of rest, was most likely first practised in Judaism, dated to the 6th century BC at the latest.

In Ancient Rome (753 BC–476 AD), every eight days there was a nundinae. It was a market day, during which children were exempted from school and agricultural workers stopped work in the field and came to the city to sell the produce of their labor or to practice religious rites.[citation needed]

The French Revolutionary Calendar (1793–1805) had ten-day weeks (called décades) and allowed décadi, one out of the ten days, as a leisure day. From 1929 to 1940, the Soviet Union utilized a calendar with five and six-day work weeks, with a rest day assigned to a worker either with a colour or number.

In cultures with a four-day workweek, the three Sabbaths derive from the culture's main religious tradition: Friday (Muslim), Saturday (Jewish, Adventist), and Sunday (Christian).

The present-day concept of the relatively longer 'week-end' first arose in the industrial north of Britain in the early 19th century and was originally a voluntary arrangement between factory owners and workers allowing Saturday afternoon off starting at 2 pm on the basis that staff would be available for work sober and refreshed on Monday morning. The Oxford English Dictionary traces the first use of the term weekend to the British magazine Notes and Queries in 1879.

In 1908, the first five-day workweek in the United States was instituted by a New England cotton mill so that Jewish workers would not have to work on the Sabbath from sundown Friday to sundown Saturday. In 1926, Henry Ford began shutting down his automotive factories for all of Saturday and Sunday, due to pressures stemming from the October Revolution,[citation needed] which witnessed the ruling class persecuted for not giving the laborers dignifying conditions. In 1929, the Amalgamated Clothing Workers of America was the first union to demand and receive a five-day workweek. The rest of the United States slowly followed, but it was not until 1940, when a provision of the 1938 Fair Labor Standards Act mandating a maximum 40-hour workweek went into effect, that the two-day weekend was adopted nationwide.

Over the succeeding decades, particularly in the 1940s to 1960s, an increasing number of countries adopted either a Friday–Saturday or a Saturday–Sunday weekend to harmonize with international markets. A series of workweek reforms in the mid-to-late 2000s and early 2010s brought much of the Arab World in synchronization with the majority of countries around the world, in terms of working hours, the length of the workweek, and the days of the weekend. The International Labour Organization (ILO) currently defines a workweek exceeding 48 hours as excessive. A 2007 study by the ILO found that at least 614.2 million people around the world were working excessive hours.
Answer: The creation of a five-day workweek in the United States came about as a result of organizing by and pressure from workers and labor groups in the first half of the 20th century, as they demanded dignified working conditions from their employers and the ruling class.