<P> The International Workingmen's Association took up the demand for an eight - hour day at its Congress in Geneva in 1866, declaring "The legal limitation of the working day is a preliminary condition without which all further attempts at improvements and emancipation of the working class must prove abortive", and "The Congress proposes eight hours as the legal limit of the working day ." </P> <P> Karl Marx saw it as of vital importance to the workers' health, writing in Das Kapital (1867): "By extending the working day, therefore, capitalist production...not only produces a deterioration of human labour power by robbing it of its normal moral and physical conditions of development and activity, but also produces the premature exhaustion and death of this labour power itself ." </P> <P> The first country to adopt eight - hour working day was Uruguay . The eight - hour day was introduced on November 17, 1915, in the government of José Batlle y Ordóñez . </P> <P> The first international treaty to mention it was the Treaty of Versailles in the annex of its thirteen part establishing the International Labour Office, now the International Labour Organization . </P>

When did the forty hour work week begin