ISO date business day add

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

Add a signed count of business days to a date, skipping caller-supplied weekend weekdays and holidays.

Use when you need to: iso date business day add · add working days to date · skip weekends and holidays.

Supported

• iso date business day add
• add working days to date
• skip weekends and holidays

Not supported

• built-in national holiday calendars
• timezones
• half-day rules
• fractional business days

Behavior

• date is a strict YYYY-MM-DD proleptic Gregorian UTC calendar date with year 0001-9999.
• days is a canonical signed integer string with absolute value at most 100000.
• weekend_days is an array of ISO weekday integers 1-7, unique, at most 6 entries. holidays is an array of unique YYYY-MM-DD dates, at most 366 entries.
• The starting date itself is never counted as a step. days=0 returns date unchanged, even if date is a weekend or holiday.
• A positive days steps forward one calendar day at a time, skipping weekend_days and holidays, until days business days have been counted. Negative days steps backward the same way.
• The call is rejected if a step would move outside year 0001-9999.

Input

• date (string, required): min length 10; max length 10; pattern ^\d{4}-\d{2}-\d{2}$
• days (string, required): max length 8; pattern ^-?(0|[1-9][0-9]*)$
• 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

• date (string, required): min length 10; max length 10

Limits

• year min: 1
• year max: 9999
• max abs days: 100000
• max weekend days: 6
• max holidays: 366

Example

Request input:

{
  "date": "2026-09-18",
  "days": "1",
  "weekend_days": [
    6,
    7
  ],
  "holidays": []
}

Response:

{
  "result": {
    "date": "2026-09-21"
  }
}

How to call it

MCP

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

{
  "id": "iso-date-business-day-add",
  "version": "1.0.0",
  "input": {
    "date": "2026-09-18",
    "days": "1",
    "weekend_days": [
      6,
      7
    ],
    "holidays": []
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-date-business-day-add/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"date":"2026-09-18","days":"1","weekend_days":[6,7],"holidays":[]}'

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

CLI

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

Get the client at /clients/cli/.

Related tools

• ISO date is business day: Test whether a date is a business day given caller-supplied weekend weekdays and holiday dates.
• ISO date add: Add a signed whole-day delta to a strict YYYY-MM-DD calendar date.
• ISO date business days count: Count the business days in an inclusive date range, skipping caller-supplied weekend weekdays and holidays.
• ISO date add months: Add a signed month count to a YYYY-MM-DD date, clamping the day to the target month.
• 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 from day of year: Convert a calendar year and ordinal day number (1-366) to a YYYY-MM-DD date.