ISO week numbering explained
Week numbers divide a year into 52 or 53 numbered weeks. While simple in concept, different standards exist for which day starts a week and how the first week of the year is defined. ISO 8601 (international standard): Weeks start on Monday. Week 1 is the week containing the year's first Thursday. This means January 1 may fall in week 52 or 53 of the previous year, and late December may be in week 1 of the next year. US convention: Weeks start on Sunday. Week 1 begins on January 1, regardless of the day of the week. This is used in the US, Canada, and some other countries. Why week numbers matter: Project management (Agile sprints are often week-based), payroll cycles, scheduling meetings ('let's meet in week 14'), logistics and delivery tracking, manufacturing production schedules, and fiscal reporting periods. Week 53: Some years have 53 weeks under the ISO standard. This happens when January 1 is a Thursday, or in leap years when January 1 is a Wednesday.
About week numbers
It's the international standard for week numbering. A week starts on Monday, and the first week of the year is the week containing the first Thursday.
Other useful tools related to date calculations
How to Use? Select a date and click calculate button. Week number according to ISO 8601 standard will be displayed.
Internationally accepted week standard
All past and future dates
Shows which year the week belongs to
Ideal for sprints and project calendars
About week numbers
It's the international standard for week numbering. A week starts on Monday, and the first week of the year is the week containing the first Thursday.