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:

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

Response:

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

How to call it

MCP

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

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

HTTP (no key)

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.

CLI

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/.

Related 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: Return the earliest and latest date in a non-empty array of YYYY-MM-DD calendar dates.
• ISO date month end: Return the last valid calendar day of the year-month of a YYYY-MM-DD date.
• 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: Return the date of the nth occurrence of an ISO weekday within a calendar month.
• ISO date to week: Convert a YYYY-MM-DD calendar date to an ISO-8601 week date.