Chronology Lab

ISO week calculator

Determine the ISO week number and year for any date so sprint reports stay in sync internationally.

Week finder

ISO

Use the calculator

Pick a date and discover which ISO week and year it belongs to. The ISO week system always starts the week on Monday and keeps week 1 as the week containing January 4.

Select a date to see the ISO week number.

Why ISO weeks?

Context

Many organizations align reporting and sprint planning to ISO weeks to avoid the uneven lengths of calendar months. ISO weeks keep each week inside a single year so data stays clean when exporting.

Pro tip: When describing deadlines, include the ISO week and year (e.g., “Deliverable due week 42, 2026”) so partners in different regions know exactly when you mean.