Does ISO Week Year upload my file or text to Tool-You servers?

No. ISO Week Year runs in this browser tab. Files stay on the device. Limit note: Local YMD to ISO week + year.

Should I use ISO Week Number instead of ISO Week Year?

Use ISO Week Year when you need ISO week number and year. Use ISO Week Number when you need ISO-8601 week and ISO year. They share a category (Date & time) but not the same job.

ISO Week Year

ISO week number and year.

Returns ISO week and ISO week-year for a local date. Unlike Simple Week Number this is ISO. Unlike ISO Week Number sibling labeling this also emphasizes year. Invalid dates fail.

What ISO Week Year does

Returns ISO week and ISO week-year for a local date. Unlike Simple Week Number this is ISO. Unlike ISO Week Number sibling labeling this also emphasizes year. Invalid dates fail.

ISO Week Year sits in the Date & time group on purpose. It is not ISO Week Number (ISO-8601 week and ISO year.) and not Simple Week Number (Simple week number with year and day-of-year.). Choose this page when you need ISO week number and year. If you stretch ISO Week Year into a neighbor’s job, the result will look wrong even though the site chrome looks the same.

How to use ISO Week Year

Confirm you need ISO Week Year, not ISO Week Number (ISO-8601 week and ISO year.). Address: /datetime/iso-week-year.
Enter the numbers or dates ISO Week Year uses. ISO week number and year.
Read the result as ISO Week Year defines it — not as Simple Week Number (Simple week number with year and day-of-year.). Returns ISO week and ISO week-year for a local date. Unlike Simple Week Number this is ISO. Unlike ISO Week Number sibling labeling this also emphasizes year. Invalid dates fail.
ISO Week Year is an estimate in the browser, not professional advice. Local YMD to ISO week + year.
Need a different formula? Try Simple Week Number (Simple week number with year and day-of-year.) instead of stretching ISO Week Year.

When not to use ISO Week Year

Skip ISO Week Year when a neighbor tool matches better — start with ISO Week Number or Simple Week Number — or when the description already warns the job will fail. In the tool’s own words: Returns ISO week and ISO week-year for a local date. Unlike Simple Week Number this is ISO. Unlike ISO Week Number sibling labeling this also emphasizes year. Invalid dates fail.

Questions about ISO Week Year

What does ISO Week Year do that other Date & time pages on this site do not?: Returns ISO week and ISO week-year for a local date. Unlike Simple Week Number this is ISO. Unlike ISO Week Number sibling labeling this also emphasizes year. Invalid dates fail. Short version: ISO week number and year.
Does ISO Week Year upload my file or text to Tool-You servers?: No. ISO Week Year runs in this browser tab. Files stay on the device. Limit note: Local YMD to ISO week + year.
Should I use ISO Week Number instead of ISO Week Year?: Use ISO Week Year when you need ISO week number and year. Use ISO Week Number when you need ISO-8601 week and ISO year. They share a category (Date & time) but not the same job.
What are the limits of ISO Week Year?: Local YMD to ISO week + year. Also: Returns ISO week and ISO week-year for a local date. Unlike Simple Week Number this is ISO. Unlike ISO Week Number sibling labeling this also emphasizes year. Invalid dates fail.