According to Marx the working day is determined by the production relations existing in the society. Each manufacturer provides a society with his own labor unit. For instance, a community working day consists of individual working hours: individual working time of each manufacturer is his unit in the community working day. The more the manufacturer gives to the society, the more he gets back. Consequently, it is more profitable for a manufacturer (a capitalist) to prolong the working day in order to give more working time to a society and earn more. Marx states that the working day consists of the obligatory working time and surplus working time and it is obvious that the working day can not be shorter, than its obligatory part while the value of surplus time can differ. In such case, it is obvious that there is a direct proportion between the value of surplus time and surplus value, which the manufacturer will get. If it is impossible to increase the obligatory time, it is possible to increase the value of surplus time. In the capitalism conditions such division is regarded as hostile and antagonistical; it causes a conflict between a manufacturer, who belongs to an upper class (bourgeoisie), and worker, who is a representative of a labor class (proletariat). As the upper class strives for the working day prolongation, the labor class strives for the restriction of the working day duration. The price, which is paid to a worker for his labor, should help the worker to restore it again so that it becomes possible to sell it the next day. The enormous length of the working day can cause the worker sell too much labor which can be restored only after several days, but the price for the labor will be the same. This would mean that the manufacturer would pay to a worker for one day, but consume the labor for three days, which obviously contradicts the agreement. This was the issue, which caused the workers’ revolts in England in the 19th century.
Finally, we see that the Marx’s studies on the working day is a fundamental aspect of capitalistic theory, and also an important moment in real life, acknowledged by some historic events, which influenced the economy of several countries.