Sunday is the day of the week between Saturday and Monday. Sunday is a day of rest in most Western countries, as a part of the weekend and weeknight. For most observant Christians, Sunday is observed as a day of worship and rest, holding it as the Lord's Day and the day of Christ's resurrection. In some Muslim countries and Israel, Sunday is the first work day of the week. According to the Hebrew calendar and traditional Christian calendars, Sunday is the first day of the week. But according to the International Organization for Standardization ISO 8601, Sunday is the seventh day of the week.