The division of the week into seven days in corresponds to the lunar cycles, lasting 4 cycles of 7 days, or month.
Since antiquity it is known by a variety of people. The Mayan calendar, for example, was made up of 13 months, 28 weeks, seven days each week. It was the lunar calendar.
However the days of the week comes from both Jewish and pagan. Each day represented a god. The Catholic Church fought the pagan names, but the campaign only took revenge on the European continent in Portugal. Was adopted (in a regimen similar to Judeo: Sabbatum press Sabbat secunda Sabbat, etc.): press feria, feria secunda, tertia, fourth, fifth, sixth, seventh hurt. Feria means "feast day", "holy day"in Latin. The Church sanctified the day of the week. After the first day given the name "Lord's Day" (Domenicus dies). By Jewish influence, the seventh is called the "seventh day", "Sabbath day" (Sabbatum). The sense of "market "that have the word "fair", remember that in medieval holy days were the market days.