PlainlyKit — Date API

PlainlyKit provides a free public Date API that adds a whole number of weeks to a given Gregorian date. The service returns the resulting date, the weekday, and the total elapsed days, all in JSON format. No API key, signup, or account is required, and the API operates over simple GET requests. It is intended for developers needing quick calendar arithmetic without authentication. The site also hosts a collection of other free online tools.

PlainlyKit — Date API is listed with 1 API on the APIs.io network. Tagged areas include Company, Date, Calendar, Free, and Public.

The PlainlyKit — Date API catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

PlainlyKit — Date API’s developer surface includes documentation and 11 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

13.6/100 emerging Agent 5/100 human only Full breakdown ↓
scored 2026-11-13 · rubric v0.28.0 · Show this score on your site →

AccessOpen

1 API

Company Date Calendar Free Public

Kin Score

Kin Score How this is scored →
scored 2026-11-13 · rubric v0.28.0

Composite quality — 13.6/100 · emerging

Contract Quality 1.4 / 21

Developer Ergonomics 1.6 / 17

Access Clarity 1.4 / 17

Operational Transparency 0.0 / 11

Contract Governance 2.2 / 10

Discoverability 5.6 / 9

Regulatory Posture 1.3 / 15

Agent readiness — 5/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document Ask about this →
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey) Ask about this →
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented) Ask about this →
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes Ask about this →
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0 Ask about this →
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented) Ask about this →

11 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 6.7 — up to +23.3 composite points Ask about this →
Access Clarity scores 8.5 — up to +18.3 composite points Ask about this →
Developer Ergonomics scores 9.5 — up to +18.1 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/plainlykit/apis.yml: open an issue on github.com/api-evangelist/plainlykit to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

Model Context Protocol (MCP)

measured — observed by APIs.io (documented)

APIs 1

Individual APIs this provider publishes, each with its own machine-readable definition.

Date API

Add weeks to a Gregorian date and get resulting date, weekday, and elapsed days. No authentication required.

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Plainlykit Context

1 classes · 4 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs. Counts are the severity each rule declares, not results of running them.

PlainlyKit — Date API API Rules

46 rules · 44 error-severity 1 warn-severity 1 info-severity

SPECTRAL

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

PlainlyKit — Date API Domain Security

TLSv1.3

SECURITY

Agentic Access (API Evangelist recommendations) 1

Recommended x-agentic-access execution contracts for AI agents.

PlainlyKit — Date API Agentic Access

1 operation

1 operations · 0 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

DataModel

Conformance

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Commercial 1

Pricing, plans, and the legal terms of use

PrivacyPolicy

PrivacyPolicy

Company 1

The organization behind the API

Website

Website

Other 2

Properties that don't map to a standard resource type

Hosts

Hosts

Vendors

Vendors

Source (apis.yml)

aid: plainlykit
name: PlainlyKit — Date API
accessModel:
  pricing: unknown
  onboarding: open
  trial: false
  try_now: false
  public: true
  gated: none
  gated_source:
  - onboarding
  label: Open access
  confidence: low
  source:
  - security
  generated: '2026-11-13'
  method: derived
image: https://plainlykit.com/social-preview.png
description: PlainlyKit provides a free public Date API that adds a whole number of weeks to a given Gregorian date. The service
  returns the resulting date, the weekday, and the total elapsed days, all in JSON format. No API key, signup, or account
  is required, and the API operates over simple GET requests. It is intended for developers needing quick calendar arithmetic
  without authentication. The site also hosts a collection of other free online tools.
url: https://artifacts.apis.io/plainlykit/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-11-08 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-11-08'
modified: '2026-11-08'
tags:
- Company
- Date
- Calendar
- Free
- Public
tags_raw:
- Company
- API
- Date
- Calendar
- Free
- Public
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: AgenticAccess
  url: agentic-access/plainlykit-agentic-access.yml
- type: Spectral
  url: rules/plainlykit-rules.yml
- type: JSONLD
  url: json-ld/plainlykit-context.jsonld
- type: Vocabulary
  url: vocabulary/plainlykit-vocabulary.yml
- type: DataModel
  url: data-model/plainlykit-data-model.yml
- type: Conformance
  url: conformance/plainlykit-conformance.yml
- type: Hosts
  url: hosts/plainlykit-hosts.yml
- type: Vendors
  url: vendors/plainlykit-vendors.yml
- type: PrivacyPolicy
  url: https://plainlykit.com/privacy
- type: DomainSecurity
  url: security/plainlykit-domain-security.yml
- type: Website
  url: https://plainlykit.com
- type: Documentation
  url: https://plainlykit.com/developers
apis:
- name: Date API
  description: Add weeks to a Gregorian date and get resulting date, weekday, and elapsed days. No authentication required.
  humanURL: https://plainlykit.com/developers
  baseURL: https://plainlykit.com
  aid: plainlykit:date-api
x-submission-notes: 'PlainlyKit is a collection of free online tools. Our public Date API adds a whole number of weeks to
  a Gregorian date and returns the resulting date, weekday, and elapsed days as JSON. No signup or API key is required.  OpenAPI
  3.1 specification: https://plainlykit.com/openapi.json Example: https://'
x-submission-probe: 2026-11-07 200 https://plainlykit.com/ ctl=404
x-enrichment:
  date: '2026-11-08'
  status: enriched
  artifacts_added: 16
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

PlainlyKit — Date API — frequently asked questions

Does PlainlyKit — Date API have an API?

Yes. APIs.io lists 1 API from PlainlyKit — Date API, including Date API.

Is the PlainlyKit — Date API ready for AI agents?

PlainlyKit — Date API has a Kin Score of 13.6 out of 100 (emerging) and an Agent Readiness score of 4.9 (human-only), scored by API Evangelist on 2026-11-13.

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