Does First Weekday of Month upload my file or text to Tool-You servers?

No. First Weekday of Month runs in this browser tab. Files stay on the device. Limit note: Year, month 1–12, ISO weekday 1–7.

Should I use Last Weekday of Month instead of First Weekday of Month?

Use First Weekday of Month when you need First Mon–Sun date in a month. Use Last Weekday of Month when you need Last Mon–Sun date in a month. They share a category (Date & time) but not the same job.

First Weekday of Month

First Mon–Sun date in a month.

Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail.

What First Weekday of Month does

Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail.

Practical limit for First Weekday of Month: Year, month 1–12, ISO weekday 1–7. That is why output can differ from heavy desktop Date & time software. Read the tool-specific note again: Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail.

How to use First Weekday of Month

Confirm you need First Weekday of Month, not Last Weekday of Month (Last Mon–Sun date in a month.). Address: /datetime/first-weekday-of-month.
Enter the numbers or dates First Weekday of Month uses. First Mon–Sun date in a month.
Read the result as First Weekday of Month defines it — not as Next Weekday (Next ISO weekday; optional include today.). Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail.
First Weekday of Month is an estimate in the browser, not professional advice. Year, month 1–12, ISO weekday 1–7.
Need a different formula? Try Next Weekday (Next ISO weekday; optional include today.) instead of stretching First Weekday of Month.

When not to use First Weekday of Month

Skip First Weekday of Month when a neighbor tool matches better — start with Last Weekday of Month or Next Weekday — or when the description already warns the job will fail. In the tool’s own words: Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail.

Questions about First Weekday of Month

What does First Weekday of Month do that other Date & time pages on this site do not?: Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail. Short version: First Mon–Sun date in a month.
Does First Weekday of Month upload my file or text to Tool-You servers?: No. First Weekday of Month runs in this browser tab. Files stay on the device. Limit note: Year, month 1–12, ISO weekday 1–7.
Should I use Last Weekday of Month instead of First Weekday of Month?: Use First Weekday of Month when you need First Mon–Sun date in a month. Use Last Weekday of Month when you need Last Mon–Sun date in a month. They share a category (Date & time) but not the same job.
What are the limits of First Weekday of Month?: Year, month 1–12, ISO weekday 1–7. Also: Finds the first local date in a month matching an ISO weekday 1–7. Unlike Last Weekday of Month this is the first match. Unlike Next Weekday this is month-scoped. Invalid inputs fail.