Does Weekday Name upload my file or text to Tool-You servers?

No. Weekday Name runs in this browser tab. Files stay on the device. Limit note: Local calendar. Long names are English only.

Should I use ISO Week Number instead of Weekday Name?

Use Weekday Name when you need Weekday name, ISO 1–7, and Sunday-based 0–6. Use ISO Week Number when you need ISO-8601 week and ISO year. They share a category (Date & time) but not the same job.

Weekday Name

Weekday name, ISO 1–7, and Sunday-based 0–6.

Prints a short or full English weekday, ISO weekday (Monday = 1), and Sunday-based 0–6. Unlike ISO Week this is not a week-of-year. Unlike Is Weekend this always names the day. Local calendar midnight. Invalid dates fail.

What Weekday Name does

Weekday Name sits in the Date & time group on purpose. It is not ISO Week Number (ISO-8601 week and ISO year.) and not Is Weekend (Weekend flag plus weekday number and name.). Choose this page when you need Weekday name, ISO 1–7, and Sunday-based 0–6. If you stretch Weekday Name into a neighbor’s job, the result will look wrong even though the site chrome looks the same.

How to use Weekday Name

Confirm you need Weekday Name, not ISO Week Number (ISO-8601 week and ISO year.). Address: /datetime/weekday.
Enter the numbers or dates Weekday Name uses. Weekday name, ISO 1–7, and Sunday-based 0–6.
Read the result as Weekday Name defines it — not as Is Weekend (Weekend flag plus weekday number and name.). Prints a short or full English weekday, ISO weekday (Monday = 1), and Sunday-based 0–6. Unlike ISO Week this is not a week-of-year. Unlike Is Weekend this always names the day. Local calendar midnight. Invalid dates fail.
Weekday Name is an estimate in the browser, not professional advice. Local calendar. Long names are English only.
Need a different formula? Try Is Weekend (Weekend flag plus weekday number and name.) instead of stretching Weekday Name.

When not to use Weekday Name

Skip Weekday Name when a neighbor tool matches better — start with ISO Week Number or Is Weekend — or when the description already warns the job will fail. In the tool’s own words: Prints a short or full English weekday, ISO weekday (Monday = 1), and Sunday-based 0–6. Unlike ISO Week this is not a week-of-year. Unlike Is Weekend this always names the day. Local calendar midnight. Invalid dates fail.

Questions about Weekday Name

What does Weekday Name do that other Date & time pages on this site do not?: Prints a short or full English weekday, ISO weekday (Monday = 1), and Sunday-based 0–6. Unlike ISO Week this is not a week-of-year. Unlike Is Weekend this always names the day. Local calendar midnight. Invalid dates fail. Short version: Weekday name, ISO 1–7, and Sunday-based 0–6.
Does Weekday Name upload my file or text to Tool-You servers?: No. Weekday Name runs in this browser tab. Files stay on the device. Limit note: Local calendar. Long names are English only.
Should I use ISO Week Number instead of Weekday Name?: Use Weekday Name when you need Weekday name, ISO 1–7, and Sunday-based 0–6. 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 Weekday Name?: Local calendar. Long names are English only. Also: Prints a short or full English weekday, ISO weekday (Monday = 1), and Sunday-based 0–6. Unlike ISO Week this is not a week-of-year. Unlike Is Weekend this always names the day. Local calendar midnight. Invalid dates fail.