Convert tools

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.

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

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

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

FAQ

ISO Week Date Converter — What are the supported inputs and limits?

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

Format references

Tool page updated: