Having a seven-day week seemed strange to sociologists since there was no corresponding geophysical event as there was with the solar day or the lunar month. They tended to attribute it to our cultures and not to biology. However, other organisms also have a seven-day cycle, and a week is, after all, a quarter of a lunar circle. At the end of the French Revolution, the revolutionary government wanted to establish a ten-day week, but the attempt failed to work. In the former Soviet Union, the rulers also experimented with modifying the week by trying five-day and six-day weeks. Again, people rejected to change the length of their week. They seemed to need to have one day out of seven in order to rest their body clocks. Weekly rhythms show up most strongly during times of stress. For the body to fight off a cold, it needs about a week. The symptoms of chicken pox show up about two weeks after the patient’s being exposed to disease. Health care workers expect to see patients with pneumonia and malaria at greatest risk after one week of fighting these diseases. By these evidences, sociologists have had reasons to reconsider their previous ideas about the origin of the seven-day week.