ISO date last weekday of month

iso-date-last-weekday-of-month · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Return the date of the last occurrence of an ISO weekday within a calendar month.

Use when you need to: iso date last weekday of month · last friday of month · final weekday in month.

Supported

• iso date last weekday of month
• last friday of month
• final weekday in month

Not supported

• nth from start (use iso-date-nth-weekday-of-month)
• timezones
• locale weekday names

Behavior

• year is a JSON integer 1-9999, month is a JSON integer 1-12.
• weekday is a JSON integer 1-7 with Monday=1 .. Sunday=7.
• Returns the date of the last time that weekday occurs in that calendar month.

Input

• year (integer, required): min 1; max 9999
• month (integer, required): min 1; max 12
• weekday (integer, required): min 1; max 7

Output

• date (string, required): min length 10; max length 10

Limits

• year min: 1
• year max: 9999

Example

Request input:

{
  "year": 2026,
  "month": 9,
  "weekday": 5
}

Response:

{
  "result": {
    "date": "2026-09-25"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "iso-date-last-weekday-of-month",
  "version": "1.0.0",
  "input": {
    "year": 2026,
    "month": 9,
    "weekday": 5
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-date-last-weekday-of-month/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"year":2026,"month":9,"weekday":5}'

The machine-readable contract is at /v1/tools/iso-date-last-weekday-of-month/versions/1.0.0.

CLI

node cli.mjs run iso-date-last-weekday-of-month 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• ISO date nth weekday of month: Return the date of the nth occurrence of an ISO weekday within a calendar month.
• ISO date month end: Return the last valid calendar day of the year-month of a YYYY-MM-DD date.
• ISO date day of year: Return the ordinal day number (1-366) of a YYYY-MM-DD date within its calendar year.
• ISO date days in month: Return the number of calendar days in a given proleptic Gregorian year and month.
• ISO date month start: Return the first calendar day of the year-month of a YYYY-MM-DD date.
• ISO date previous weekday: Return the most recent date on or before a given date that falls on a specified ISO weekday.