Date & Time

Week Number Calculator

Find a calendar date’s week number, week year and weekday using ISO 8601 or Sunday-start weeks.

Keep this tool in your workbenchReport a problem

Loading Date & Time controls…

What does this tool do?

Find a calendar date’s week number, week year and weekday using ISO 8601 or Sunday-start weeks. Inputs: Date, Week convention. Outputs: Week number, Week year, Day of week.

How to use it?

Enter a date and select its week-numbering convention. Choose “Calculate week number”, then copy individual result values. Clear removes all inputs and results and restores option defaults.