Does this date fall on the claimed weekday? (batch, year boundaries and leap days)

$0.005 USDC per call · Business, finance and compliance · POST /api/v1/date-claim-check · Id date-claim-check

Checks up to 200 claims 'Monday 2026-12-28' against the proleptic Gregorian calendar and reports the real weekday, whether the date exists (2026-02-29 does not), and the nearest date carrying the claimed weekday; a claim 'Friday, 13 March' without a year returns the years in a range where it holds. Built for an agent verifying dates in a document, email or itinerary. Gregorian only (no Julian dates before 1582 reform), no time zones, and it does not guess which year was meant.

What you get

Wrong weekday-date pairs are the commonest hallucinated date error; one call checks a whole itinerary.

Call it

Send the JSON body below to https://agents.writerslogic.com/api/v1/date-claim-check. An unpaid request answers 402 with the price and how to pay; a request that fails with a 5xx status is not charged.

curl -i -X POST https://agents.writerslogic.com/api/v1/date-claim-check \
  -H 'content-type: application/json' \
  -d '{"items":[{"date":"2026-12-28","weekday":"Monday"},{"date":"2027-01-01","weekday":"Thursday"},{"date":"2026-02-29","weekday":"Sunday"}]}'

Input

Example request body

{
  "items": [
    {
      "date": "2026-12-28",
      "weekday": "Monday"
    },
    {
      "date": "2027-01-01",
      "weekday": "Thursday"
    },
    {
      "date": "2026-02-29",
      "weekday": "Sunday"
    }
  ]
}

Result

The response is { "data": ..., "_provenance": ... }. data carries these fields; _provenance is a signed W3C Verifiable Credential with a C2PA-style manifest, checked free at POST /api/v1/verify-provenance.

Pay and connect

Available through: x402 (USDC on Base), MCP. MCP clients reach it through the calendar-deadline-kit package.

Machine-readable

• This agent as JSON (schemas, example, OpenAPI operation)
• Free signed sample response
• OpenAPI 3.1 · Catalog · Index of every agent