Does ISO Ordinal Date upload my file or text to Tool-You servers?

No. ISO Ordinal Date runs in this browser tab. Files stay on the device. Limit note: Local YMD to YYYY-DDD. Invalid dates fail.

Should I use Day of Year instead of ISO Ordinal Date?

Use ISO Ordinal Date when you need YYYY-DDD ordinal date. Use Day of Year when you need Ordinal day 1–366 plus remaining days in the year. They share a category (Date & time) but not the same job.

ISO Ordinal Date

YYYY-DDD ordinal date.

Formats a local date as YYYY-DDD ordinal. Unlike Day of Year this includes the year prefix. Unlike ISO Week Number this is not week-based. Invalid dates fail.

What ISO Ordinal Date does

Formats a local date as YYYY-DDD ordinal. Unlike Day of Year this includes the year prefix. Unlike ISO Week Number this is not week-based. Invalid dates fail.

The interactive controls for ISO Ordinal Date load after this article so crawlers still read the instructions. Path /datetime/iso-ordinal is the canonical address. Work happens on this device; Tool-You does not take a copy of the file or pasted text for ISO Ordinal Date.

How to use ISO Ordinal Date

Confirm you need ISO Ordinal Date, not Day of Year (Ordinal day 1–366 plus remaining days in the year.). Address: /datetime/iso-ordinal.
Enter the numbers or dates ISO Ordinal Date uses. YYYY-DDD ordinal date.
Read the result as ISO Ordinal Date defines it — not as ISO Week Number (ISO-8601 week and ISO year.). Formats a local date as YYYY-DDD ordinal. Unlike Day of Year this includes the year prefix. Unlike ISO Week Number this is not week-based. Invalid dates fail.
ISO Ordinal Date is an estimate in the browser, not professional advice. Local YMD to YYYY-DDD. Invalid dates fail.
Need a different formula? Try ISO Week Number (ISO-8601 week and ISO year.) instead of stretching ISO Ordinal Date.

When not to use ISO Ordinal Date

Skip ISO Ordinal Date when a neighbor tool matches better — start with Day of Year or ISO Week Number — or when the description already warns the job will fail. In the tool’s own words: Formats a local date as YYYY-DDD ordinal. Unlike Day of Year this includes the year prefix. Unlike ISO Week Number this is not week-based. Invalid dates fail.

Questions about ISO Ordinal Date

What does ISO Ordinal Date do that other Date & time pages on this site do not?: Formats a local date as YYYY-DDD ordinal. Unlike Day of Year this includes the year prefix. Unlike ISO Week Number this is not week-based. Invalid dates fail. Short version: YYYY-DDD ordinal date.
Does ISO Ordinal Date upload my file or text to Tool-You servers?: No. ISO Ordinal Date runs in this browser tab. Files stay on the device. Limit note: Local YMD to YYYY-DDD. Invalid dates fail.
Should I use Day of Year instead of ISO Ordinal Date?: Use ISO Ordinal Date when you need YYYY-DDD ordinal date. Use Day of Year when you need Ordinal day 1–366 plus remaining days in the year. They share a category (Date & time) but not the same job.
What are the limits of ISO Ordinal Date?: Local YMD to YYYY-DDD. Invalid dates fail. Also: Formats a local date as YYYY-DDD ordinal. Unlike Day of Year this includes the year prefix. Unlike ISO Week Number this is not week-based. Invalid dates fail.