# 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:

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

Response:

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

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

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

### HTTP (no key)

```sh
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](/v1/tools/iso-date-last-weekday-of-month/versions/1.0.0).

### CLI

```sh
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/](/clients/cli/).

## Related tools

- [ISO date nth weekday of month](/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](/tools/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](/tools/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](/tools/iso-date-days-in-month): Return the number of calendar days in a given proleptic Gregorian year and month.
- [ISO date month start](/tools/iso-date-month-start): Return the first calendar day of the year-month of a YYYY-MM-DD date.
- [ISO date previous weekday](/tools/iso-date-previous-weekday): Return the most recent date on or before a given date that falls on a specified ISO weekday.