# ISO date weekday occurrences in range

`iso-date-weekday-occurrences-in-range` · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

List every date within an inclusive date range that falls on a given ISO weekday.

**Use when you need to: iso date weekday occurrences in range · every monday between two dates · list matching weekdays in range.**

## Supported

- iso date weekday occurrences in range
- every monday between two dates
- list matching weekdays in range

## Not supported

- multiple weekdays per call
- timezones
- locale weekday names
- recurring rules with exceptions

## Behavior

- start and end are strict YYYY-MM-DD calendar dates with year 0001-9999. start must not be after end.
- weekday is a JSON integer 1-7 with Monday=1 .. Sunday=7.
- end minus start must not exceed 36600 days (about 100 years).
- dates lists every date d with start <= d <= end whose ISO weekday equals weekday, in ascending order.

## Input

- `start` (string, required): min length 10; max length 10; pattern `^\d{4}-\d{2}-\d{2}$`
- `end` (string, required): min length 10; max length 10; pattern `^\d{4}-\d{2}-\d{2}$`
- `weekday` (integer, required): min 1; max 7

## Output

- `dates` (array of string, required): each min length 10; each max length 10

## Limits

- year min: 1
- year max: 9999
- max range days: 36600
- max occurrences: 5230

## Example

Request input:

```json
{
  "start": "2026-09-01",
  "end": "2026-09-30",
  "weekday": 1
}
```

Response:

```json
{
  "result": {
    "dates": [
      "2026-09-07",
      "2026-09-14",
      "2026-09-21",
      "2026-09-28"
    ]
  }
}
```

## How to call it

### MCP

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

```json
{
  "id": "iso-date-weekday-occurrences-in-range",
  "version": "1.0.0",
  "input": {
    "start": "2026-09-01",
    "end": "2026-09-30",
    "weekday": 1
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/iso-date-weekday-occurrences-in-range/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"start":"2026-09-01","end":"2026-09-30","weekday":1}'
```

The machine-readable contract is at [/v1/tools/iso-date-weekday-occurrences-in-range/versions/1.0.0](/v1/tools/iso-date-weekday-occurrences-in-range/versions/1.0.0).

### CLI

```sh
node cli.mjs run iso-date-weekday-occurrences-in-range 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [ISO date range list](/tools/iso-date-range-list): Enumerate the dates in an inclusive [start, end] range stepped by a whole number of days.
- [ISO date age](/tools/iso-date-age): Compute the calendar-aware elapsed years, months, and days between a birth date and an as-of date.
- [ISO date business days count](/tools/iso-date-business-days-count): Count the business days in an inclusive date range, skipping caller-supplied weekend weekdays and holidays.
- [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 range intersect](/tools/iso-date-range-intersect): Compute the intersection of two inclusive [start, end] date ranges.
- [ISO date compare](/tools/iso-date-compare): Compare two YYYY-MM-DD calendar dates and return -1, 0, or 1.