The concept of working time emerged with the industrial revolution, when industrialisation led to workers being grouped together in the same place and synchronising their working and non-working time. From the end of the 19th century, the legislature adopted a system designed to limit working hours within limits compatible with what the human body could cover. Contemporary working time law pursues multiple objectives. However, the effectiveness and effectiveness of the legal system has been undermined. In some cases, the ineffectiveness of the law is a sign of a call for other rules or delimitation of working time. In other cases, failure to apply the law reflects a challenge to the legal protection model. Deindustrialisation and the development of services and digitalisation have led to a fragmentation of places and working time. Management methods based on the autonomy of workers and the result of performance, the desire of employees themselves to have greater control over their time, encouraged by the International Labour Organisation, lead to a challenge to the relevance of working time as an instrument for measuring the volume of work of a number of workers, while the European Union requires better monitoring of the work carried out on a daily basis by employees. While work has changed, the way it is measured has not changed. Several avenues are being explored to try to organise the protection of employees against excessive work, which is no longer fully guaranteed by the law as it is designed.