ISO date is business day

iso-date-is-business-day · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Test whether a date is a business day given caller-supplied weekend weekdays and holiday dates.

Use when you need to: iso date is business day · is date a working day · business day check with holidays.

Supported

• iso date is business day
• is date a working day
• business day check with holidays

Not supported

• built-in national holiday calendars
• timezones
• half-day rules

Behavior

• date is a strict YYYY-MM-DD proleptic Gregorian UTC calendar date with year 0001-9999.
• weekend_days is an array of ISO weekday integers 1-7 (Monday=1 .. Sunday=7), unique, with at most 6 entries (at least one non-weekend weekday must remain).
• holidays is an array of unique YYYY-MM-DD dates, at most 366 entries. No built-in holiday calendar is used; only caller-supplied dates count.
• is_business_day is false if the ISO weekday of date is in weekend_days, or if date is listed in holidays; otherwise true.

Input

• date (string, required): min length 10; max length 10; pattern ^\d{4}-\d{2}-\d{2}$
• weekend_days (array of integer, required): max items 6; each min 1; each max 7
• holidays (array of string, required): max items 366; each min length 10; each max length 10

Output

• is_business_day (boolean, required)

Limits

• year min: 1
• year max: 9999
• max weekend days: 6
• max holidays: 366

Example

Request input:

{
  "date": "2026-09-19",
  "weekend_days": [
    6,
    7
  ],
  "holidays": []
}

Response:

{
  "result": {
    "is_business_day": false
  }
}

How to call it

MCP

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

{
  "id": "iso-date-is-business-day",
  "version": "1.0.0",
  "input": {
    "date": "2026-09-19",
    "weekend_days": [
      6,
      7
    ],
    "holidays": []
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-date-is-business-day/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"date":"2026-09-19","weekend_days":[6,7],"holidays":[]}'

The machine-readable contract is at /v1/tools/iso-date-is-business-day/versions/1.0.0.

CLI

node cli.mjs run iso-date-is-business-day 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• ISO date business day add: Add a signed count of business days to a date, skipping caller-supplied weekend weekdays and holidays.
• ISO date is leap year: Test whether a proleptic Gregorian calendar year is a leap year.
• ISO date business days count: Count the business days in an inclusive date range, skipping caller-supplied weekend weekdays and holidays.
• ISO date range contains: Test whether an inclusive [start, end] date range contains a given date.
• ISO date add years: Add a signed whole-year delta to a YYYY-MM-DD date, clamping the day if 29 February has no match.
• ISO date day of year: Return the ordinal day number (1-366) of a YYYY-MM-DD date within its calendar year.