Worktime regulations vary in different countries. So, the number of days you can work in a row depends on the regulations in your country of residence or region of employment. For example, in the European Union and the United Kingdom, the law prohibits working more than an average of 48 hours a week if you are over 18 years old, while those below this age are limited to 40 hours. However, there is a voluntary opt-out for those who need it.