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ISO Week Date Converter

Convert Gregorian dates to ISO week-year, week and weekday and back.

Convert in your browser · No sign-up

Weeks start Monday; week 1 contains January 4. Week-year may differ from calendar year. Invalid week 53 values are rejected.

Up to 100,000 UTF-16 units per input and 1,000,000 per result. See the supported formats and examples below.

Result

Add your input or load an example, then run the tool. Your result will appear here.

How to use

  1. Convert Gregorian dates to ISO week-year, week and weekday and back.
  2. Choose the mode or options, then run the tool.
  3. Review the result, then copy or download the TXT file.

Example

2021-01-01 ⇄ 2020-W53-5

Details and limitations

Text stays in your browser; it is not sent to a conversion server.

Format references

Tool page updated: