# ISO date week bounds

`iso-date-week-bounds` · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Return the Monday and Sunday of the ISO-8601 week that contains a calendar date.

**Use when you need to: iso date week bounds · monday and sunday of an iso week · iso week start and end dates.**

## Supported

- iso date week bounds
- monday and sunday of an iso week
- iso week start and end dates

## Not supported

- locale week numbers
- Sunday-first weeks
- month start and end
- timezones
- datetime input
- fiscal weeks

## Behavior

- Input date is a strict YYYY-MM-DD proleptic Gregorian UTC calendar date with year 0001-9999.
- ISO weeks start on Monday and end on Sunday.
- start is that week’s Monday and end is that week’s Sunday, each as YYYY-MM-DD.
- Both start and end must stay in years 0001-9999; otherwise the call is rejected.

## Input

- `date` (string, required): min length 10; max length 10; pattern `^\d{4}-\d{2}-\d{2}$`

## Output

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

## Limits

- year min: 1
- year max: 9999
- date length: 10

## Example

Request input:

```json
{
  "date": "2026-01-08"
}
```

Response:

```json
{
  "result": {
    "start": "2026-01-05",
    "end": "2026-01-11"
  }
}
```

## How to call it

### MCP

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

```json
{
  "id": "iso-date-week-bounds",
  "version": "1.0.0",
  "input": {
    "date": "2026-01-08"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/iso-date-week-bounds/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"date":"2026-01-08"}'
```

The machine-readable contract is at [/v1/tools/iso-date-week-bounds/versions/1.0.0](/v1/tools/iso-date-week-bounds/versions/1.0.0).

### CLI

```sh
node cli.mjs run iso-date-week-bounds 1.0.0 --input input.json --base-url https://computefirst.net
```

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

## Related tools

- [ISO date quarter bounds](/tools/iso-date-quarter-bounds): Return the calendar quarter number and the first/last dates of the quarter containing a date.
- [ISO date min max](/tools/iso-date-min-max): Return the earliest and latest date in a non-empty array of YYYY-MM-DD calendar dates.
- [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 month start](/tools/iso-date-month-start): Return the first calendar day of the year-month of a YYYY-MM-DD date.
- [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 to week](/tools/iso-date-to-week): Convert a YYYY-MM-DD calendar date to an ISO-8601 week date.