Date calculator API: add days, months or business days to a date

$0.01 per call · failed calls are never charged · no account or subscription: pay per call with a card key or USDC

Add (or subtract, with negative numbers) years, months, weeks, days, hours and minutes to a date, or add business days (skipping Saturdays and Sundays). Month ends are clamped (31 Jan + 1 month = 28/29 Feb). Use to compute due dates and expiries.

When to use it

Compute due dates and expiries
Add or subtract years, months, weeks, days, hours and minutes
Add business days, skipping Saturdays and Sundays

Run it free (25 free calls) Buy credits by card (from $1) Example result (JSON)

Inputs

Name	Type	Description
`date` (required)	string	Start date or ISO timestamp
`years`	integer	Years to add (negative subtracts)
`months`	integer	Months to add
`weeks`	integer	Weeks to add
`days`	integer	Days to add
`hours`	integer	Hours to add
`minutes`	integer	Minutes to add
`businessDays`	integer	Weekdays to add (skips weekends)

Request

Over HTTP, with a card key from /credits:

curl -H "Authorization: Bearer adt_…" "https://tools.funwords.eu/date/add?date=2026-01-31"

Or one of your 25 free calls, no key:

curl "https://tools.funwords.eu/date/add?date=2026-01-31&trial=1"

Without a key, the same URL answers 402 Payment Required with x402 and MPP terms, so an agent with a wallet pays per call in USDC (Base, Polygon, Arbitrum or Solana over x402; Base or Tempo over MPP) and retries.

Example result

{
  "result": "2026-02-28T00:00:00.000Z",
  "date": "2026-02-28",
  "weekday": "Saturday"
}

From an AI agent (MCP)

Add the MCP server to Claude, Cursor or any MCP client. This tool is date_add, and the first 25 successful calls are free:

https://tools.funwords.eu/mcp

Questions

What about month ends?

They are clamped: 31 Jan + 1 month = 28/29 Feb.

Are public holidays skipped?

No, only Saturdays and Sundays; /holidays lists a country's holidays.

How do I pay?

Each successful call costs $0.01; failed calls are not charged. The first 25 calls are free. Then pay with card credits (from $1; the key goes in an Authorization header or, for clients that can only fetch a URL, as api_key= in the URL) or per call in USDC over x402 or MPP. No account is needed.