The week is probably the most synthetic measure of time, as it is not based on planetary rotation, but subjective definition. How has it affected society?
This is a very broad and interesting question! I will try to contribute through my area of expertise, which lies in occupational psychology. There are some studies that provide evidence for day-of-week effects such as better mood on weekends and Fridays (Stone, Schneider, & Harter, 2012). This effect was diminished for retired and older people. Consistent with this study Helliwell and Wang (2011) found increased happiness, enjoyment, and laughter, and less anxiety, sadness, and anger on weekends. For full-time paid workers this effect was twice as large.
So, one might infer from these studies that if for example the weekend would only consist of one day stress levels would be increased as there is less time for recovery. However, one should bear in mind that some are not as affected by the week as others such as the retired. So maybe it is more meaningful to investigate the concept of the (seven-day) week for specific population groups.
Article Day-of-week mood patterns in the United States: On the exist...