DST gap and overlap check for local times and stated offsets in an IANA zone

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

Checks up to 100 local date-times (YYYY-MM-DDTHH:MM) or offset timestamps against an IANA time zone and reports whether each wall time exists once, never (spring-forward gap) or twice (fall-back overlap), with every real instant and the offset in force; also lists a zone's offset transitions in a year. Built for an agent scheduling a meeting, cron job or deadline in someone else's zone. Uses the runtime's ICU tzdata (version reported), not a table of ours; it does not choose a resolution for you unless you ask via business-deadline, and does not read the clock.

What you get

A 02:30 job on the second Sunday of March in New York never fires; 01:30 in November fires twice.

Call it

Send the JSON body below to https://agents.writerslogic.com/api/v1/dst-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/dst-check \
  -H 'content-type: application/json' \
  -d '{"items":[{"timeZone":"America/New_York","local":"2026-03-08T02:30"},{"timeZone":"America/New_York","local":"2026-11-01T01:30"}],"transitionsIn":{"timeZone":"America/New_York","year":2026}}'

Input

Field	Type	Required	Description
`items`	array<object>; max 100 items	yes
`transitionsIn`	object	no

Example request body

{
  "items": [
    {
      "timeZone": "America/New_York",
      "local": "2026-03-08T02:30"
    },
    {
      "timeZone": "America/New_York",
      "local": "2026-11-01T01:30"
    }
  ],
  "transitionsIn": {
    "timeZone": "America/New_York",
    "year": 2026
  }
}

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.

Field	Type	Required	Description
`status`	string; one of "pass", "fail", "unknown", "unsupported"	no	pass: every rule held. fail: a rule was violated (see witnesses). unknown: the input lacks the evidence to decide. unsupported: outside what this engine covers. Missing evidence is never a pass.
`items`	array<object>	no
`transitions`	array<object>	no
`witnesses`	array<object>	no
`versions`	object	no	Every semantic dependency of this answer (engine, tables and their as-of dates, tokenizer, calendar, rounding profile).
`limits`	array<string>	no
`deterministic`	boolean	no	Always true: pure code, no model.

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
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