OpenAPI documentation and free-tier pricing

Short answer: the direct OpenAPI contract is at /openapi-direct.yaml and drives the API reference. Every plan uses that same contract, starting with a Free plan of 10,000 requests a month.

Where are the API contract and plans?

The API reference is generated from the direct OpenAPI contract and provides time API OpenAPI documentation with endpoint guides, request parameters, sample responses, and downloadable YAML. The documentation explains authentication, selectors, bulk mode, signed responses, errors, and best practices.

How do I use the OpenAPI contract in a project?

Download the direct contract from the reference page or open /openapi-direct.yaml directly. Treat the contract as the source for paths, parameters, response schemas, and security requirements. Keep a copy pinned to the version your integration was tested against and regenerate or update clients when the contract changes.

The WorldTimeAPI-compatible /api/* routes are described in a separate contract, /openapi-worldtimeapi.yaml, with its own interactive reference.

The direct API uses a server-side Bearer key. RapidAPI is a separate marketplace transport and uses X-RapidAPI-Key plus X-RapidAPI-Host; do not mix those authentication headers with direct requests.

What do the plans and quotas include?

The direct catalog includes a Free plan with 10,000 requests per month, making it a time API with free tier for trying the contract, followed by Starter, Growth, and Scale monthly plans. All plans use the same endpoint contract; quotas and prices are shown on pricing. RapidAPI remains a separate marketplace transport with its own subscription and headers.

Plan limits are entitlement metadata, not a different API version. Build your client to handle quota responses and expose the current plan in your account tooling instead of hard-coding a plan-specific endpoint list.

A practical integration path

1. Read getting started and create a direct key.
2. Download the OpenAPI contract and choose an endpoint from the reference.
3. Exercise the request with a test timezone or timestamp before wiring user input into selectors.
4. Add structured handling for documented 4xx validation responses and transient 5xx responses.
5. Add signed responses when the caller needs to verify body integrity independently.

It is a REST time API and a JSON time API end to end: plain HTTPS requests in, JSON out.

Related guides and documentation

• SDK usage guide: clients generated from this contract.
• World Time API guide: your first request.
• WorldTimeAPI alternative: the compatible routes and their contract.
• See pricing, the documentation and the API reference.