In most countries in the West, the workweek is Monday through Friday, with Saturday and Sunday considered the weekend. Most people also consider Friday evening to be part of the weekend.
The modern idea of the weekend came from the Jewish tradition of the Sabbath. In some Christian denominations, Sunday is set aside for worship and resting. Although the Christian Sabbath is just one day, Sunday, the traditional time for rest, starting in the 20th century, also encompassed the Jewish Sabbath, which is from Friday evening to Saturday evening. The weekend in most countries where the majority of people are Muslim is typically Thursday and Friday, or Friday and Saturday.