You will often hear historians talk about working hours. They explain how Trade Unions and Socialist campaigners brought about a much reduced work day. That happened mostly over the 19th century and the 20th century. This is true, but I think the presentations of it tend to be myopic.
In the early 19th century across the whole world people were very poor by modern standards. Due to the Industrial Revolution that changed and in Europe wages increased significantly. In the UK wages in 1900 were more than twice what they had been in 1800. That's in real terms, adjusted for inflation.
Some workers campaigned for shorter working hours because they could afford it. Of course, if working hours are lower then total wages are too. Everyone knew this. By the end of the 19th century wages had risen enough that many workers were prepared to sacrifice lower total wages for more leisure time. The labour organizations would never have successfully talked their members into these campaigns unless those members were in this situation. As growth continued in the 20th century and spread to other countries there were more and more people willing to sacrifice some wage for more free time.
Suppose that there had been a law in, say, 1770 which forced people to work less than 35 hours per day. In that case many people would probably have flouted the law because their incomes were so low that they considered more work necessary to buy things. Similarly, if people find the standard working week too long then they can search out employers who offer part-time work which covers a shorter part of the week.
It's worth mentioning that in a sense, employers never control the amount of time worked. Employment contracts may specify an amount of working time, but people can leave employment. It has always been possible to work for a few years, then quit your job and enjoy some leisure time. Then take up another job. Economists call changes to the number of hours worked over the short-run changes to the intensive margin. The changes to the number of hours worked over the long-run are changes to the extensive margin - changes that come about from the decision to work or not. Of course, this doesn't mean that changes to the intensive margin are irrelevant. When the labour campaigners succeeded in bringing down weekly working hours they really did change things for many workers. Quitting jobs and restarting is inconvenient and risky in times of high unemployment. Of course, some people don't have the willpower to save up for long periods of time either. However, it's also true that changes to the length of the full-time working week probably have much less effect on total working hours than people think. For example, people will tell you that the standard working week in the US is 40 hours. In a sense this is true for full-time employees. Despite that though, working hours have continued to fall from the 1950s to the present day. This is partially because of part-time work, but also because of people taking time off by quitting.
