week

The week is a unit of time consisting of seven days, used in most civil calendars to organize recurring time cycles. It provides a regular rhythm for work, study, worship, and social activities, repeating every seven days.

The seven-day cycle has ancient origins in Mesopotamian and other Near Eastern calendars and was adopted by various cultures over centuries. Many languages name the days after celestial bodies or deities: Sunday (sun), Monday (moon), Tuesday (named for a Norse god associated with Mars), Wednesday (Woden or Mercury), Thursday (Thor or Jupiter), Friday (Frigg or Venus), and Saturday (Saturn). The modern week spread through the Roman Empire and gained dominance in Europe with the spread of Christianity and later global trade. Some historical calendars used other week lengths before standardization.

In contemporary international use, standards such as ISO 8601 define Monday as the first day of the week, and establish a week date system in which Week 1 is the week containing the year's first Thursday. Week numbering is widely used in business, administration, and scheduling. Regional practices vary: some cultures begin the week on Sunday, others on Saturday, and weekend patterns differ, with two days off typically observed on Saturday–Sunday or Friday–Saturday in certain regions and configurations.

The week underpins calendars, planning tools, educational terms, and religious observances, providing a predictable framework for time management. While the seven-day week is nearly universal, local conventions regarding the week's start and the days off reflect cultural and religious differences.