Why are there seven days in a week?

The Hebrew and Christian Bible says that the world was created in six days, and the seventh day was a day of rest. For that reason Jews and Christians long ago arranged their lives according to a seven-day rhythm. Finally, calendars were made with the days in seven columns marking off weeks. Nearly two thousand years ago, Christian beliefs began to spread throughout Europe, along with the seven-day cycle. Later, when Europeans settled in North and South America. the seven-day week went with them. Still later very powerful businesses grew up in Europe and the United States. Business offices were almost always closed on the Sabbath, which was the first day of the week according to the European calendar.