A calendar week is the standard 7-day cycle used to measure weeks within a year. The first day is Monday under ISO 8601 and Sunday under the US convention.
Calendar week vs working week
A calendar week always counts 7 days. A working week counts only business days, typically 5. Payroll, leave accruals, and shift rosters use the working week. Week numbering, scheduling, and reporting use the calendar week.
Where calendar weeks appear
Calendar weeks anchor 3 common business activities:
- Scheduling — meeting cadences, editorial calendars, and academic timetables.
- Sprint cadence — agile teams plan 1-week or 2-week sprints aligned to calendar week boundaries.
- Reporting — finance, retail, and operations dashboards aggregate metrics by calendar week for trend analysis.
The first and last day of a calendar week depend on the standard. ISO 8601 sets Monday as day 1 and Sunday as day 7. The US convention sets Sunday as day 1 and Saturday as day 7. Australian payroll and retail systems use both, depending on vendor.