established · -0.2 capabilitymarket resourcedomain

Calendar

Score 25.0 / 100 53 providers +68 via APIs 102 APIs Search apis.io →
Business capabilities this tag reaches
Travel Revenue & Yield Management 1 Patient Access Management 1 Payments & Card Management 1
Variants seen in the corpus: CalendarsCalendar

Providers using this tag (53)

Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.

Exemplar 2 Complete, well-documented, and agent-ready
NylasCommunicationsContactsEmail2 APIs93.2CycleCalcsAstronomySpaceScienceEphemeris1 API67.0
Strong 6 Solid coverage with minor gaps
Chili PiperSchedulingLead RoutingMeetingsSales19 APIs66.0Microsoft OutlookContactsEmailEnterprise1 API66.0Google WorkspaceCollaborationEmailProductivity1 API60.5Microsoft ExchangeCollaborationContactsEmail6 APIs58.3Amazon WorkMailBusiness CommunicationEmailEnterprise1 API57.1CalendarificPublic APIsHolidaysWorldwide1 API54.3
Developing 8 Usable, with meaningful gaps to close
Checkiday - National Holiday and Event APIHolidaysEventObservances1 API52.1MeetsMoreCompanyMarketplaceLocal ServicesHome Services2 APIs47.8Holiday APIHolidaysPublic HolidaysObservances1 API47.7Google CalendarAvailabilityEventGoogle1 API46.3API Calendrier Marocain | Jours Fériés & Ouvrables REST + SDK PythonHolidaysMoroccoBusiness Days2 APIs44.4SavvyCalSchedulingAppointmentsAvailability1 API43.4Reclaim.aiArtificial IntelligenceSchedulingProductivity1 API42.4CalendlyAppointmentsAutomationBooking1 API40.7
Thin 10 Limited public surface area
Zoho MailEmailMailCollaborationMessaging1 API39.0Microsoft 365ProductivityCollaborationEmail1 API38.0LumaEventEvent ManagementTicketingCommunity1 API37.5CronofySchedulingAvailabilityBooking1 API37.0Cal.comProductivitySchedulingOpen Source1 API36.9SpurwingSchedulingAppointmentsBooking1 API28.9Acuity SchedulingAppointment SchedulingBookingScheduling1 API28.5AmieCompanyConsumerProductivity28.4DoodleSchedulingMeetingsGroup Polls1 API27.5ZimbraEmailCollaborationMessaging1 API27.2
Emerging 7 Early or largely undocumented
ZcalSchedulingBookingMeetings1 API25.4NorishCompanyRecipesMeal PlanningGroceries1 API24.5SupafaxCompanyEmailAI Assistant19.3CronCompanyConsumerScheduling15.8CabinetCompanySchedulingExecutive Assistant13.2AWSTCompanyProductivitySchedulingDocument Management12.2VelaCompanySchedulingArtificial IntelligenceAI Agents11.4
Minimal 20 Almost no public developer surface
SaturnCompanySchedulingConsumer9.7TownCompanyArtificial IntelligenceAgentsPersonal Assistant6.3Hebrew CalendarPublic APIs1 API6.0UK Bank HolidaysPublic APIs1 API6.0Church CalendarPublic APIs1 API5.1LectServePublic APIs1 API5.1Nager.DatePublic APIs1 API5.1Namedays CalendarPublic APIs1 API5.1Non-Working DaysPublic APIs1 API5.1Public HolidaysPublic APIs1 API5.1Festivo Public HolidaysPublic APIs1 API4.6Czech Namedays CalendarPublic APIs1 API4.1Non-Working DaysPublic APIs1 API3.5Russian CalendarPublic APIs1 API3.5TimeBlocksCompanySchedulingProductivity3.4AcompliCompanyEmailMobileProductivity2.5ScoopCompanyFuture Of WorkHybrid WorkWorkplace Scheduling2.5ClockwiseArtificial IntelligenceSchedulingFocus Time1 API0.0IRLCompanySocialMessagingEvent0.0Woven SoftwareCompanySchedulingProductivity0.0

APIs with this tag (100)

Ranked by the provider's API Evangelist rating — the Kin Score is scored per provider, not per API, so every API of a provider shares its band. How the rating works →

Exemplar 7 Complete, well-documented, and agent-ready
Nylas Calendar APIThe Nylas Calendar API allows you to create and manage calendars, and access the events they contain. Nylas...93.2ActiveCampaign Calendars APIThe Calendars API from ActiveCampaign — 2 operation(s) for calendars.77.6Google Calendars APIOperations related to Calendars70.1Microsoft Calendar APIAccess and manage Outlook calendar events69.2ZnanyLekarz Calendars APISimple operations on the calendar belonging to the address68.1CycleCalcs MCP ServerHosted stateless Streamable HTTP MCP server exposing 11 astronomy tools backed by the v2 REST endpoints. To...67.0AlphaAI Calendar APIScheduled US macro releases (FOMC, CPI, jobs, GDP, PCE…).66.7
Strong 20 Solid coverage with minor gaps
HighLevel Calendars APIDocumentation for Calendars API66.4Cisco XDR Calendars APIThe Calendars API from Cisco XDR — 3 operation(s) for calendars.65.6Zoho CalendarThe Zoho Calendar API provides REST endpoints to customize calendar features, allowing you to manage calend...65.1Unified.to Calendar APIThe calendar API from Unified.to — 11 operation(s) for calendar.64.9Bentley Systems Calendars APICalendars resources for the iTwin Schedules API.63.8Microsoft Office 365 Calendar APIAccess and manage Outlook calendar events, calendars, and calendar groups. Supports scheduling, meeting man...61.9Outlook Calendar APIAccess and manage calendar events, meeting requests, and calendar groups.61.9Clear Street Calendar APIAccess clocks and financial calendars for market sessions and events.60.5Google Calendar APICreate and manage calendars, events, and attendees.60.5Google Workspace APIs Calendar APIThe Calendar API from Google Workspace APIs — 3 operation(s) for calendar.60.5ThetaData Calendar APIThe Calendar API from ThetaData — 3 operation(s) for calendar.59.8Microsoft Exchange Calendars APIOperations for managing calendars58.3Charthop Calendar APIThe calendar API from Charthop — 10 operation(s) for calendar.58.1EODHD Calendar APICalendar events including earnings, IPOs, splits, dividends, and trends57.4EODHD Economic Events Calendar APIProvides a global economic calendar of macroeconomic releases including country, event name, scheduled time...57.4Zoom Calendar APIThe Zoom Calendar API enables developers to manage calendar events, automate scheduling, sync across platfo...55.8Alpaca Calendar APIThe Calendar API from Alpaca — 2 operation(s) for calendar.55.4Trakt Calendars APIUpcoming and recently aired schedules for shows, episodes, and movies.55.2Outlook Mail APIAPI for accessing and managing email, calendar, contacts, and tasks in Outlook.54.9KISI Calendars APIThe Calendars API from KISI — 1 operation(s) for calendars.54.8
Developing 28 Usable, with meaningful gaps to close
Clio Calendars APICalendars contain Calendar Entries. All Clio accounts contain one firm Calendar ("AccountCalendar"), person...53.3Everbridge Calendars APIEB Suites - Calendars Management53.3Blue Prism Calendars APIThe Calendars API from Blue Prism — 8 operation(s) for calendars.52.2SAP BI Tools Calendars APIManage calendar events and tasks used for planning workflows and scheduling in SAP Analytics Cloud.52.2SIC Clearing Day Calendar APIScheduling information for the electronic payment services provided by SIX Interbank Clearing Ltd - clearin...51.1Hostaway Calendar APIRead and update the per-listing availability and nightly pricing calendar. Supports per-day retrieval, batc...51.0VaultRE Calendar APIOperations related to calendar events50.3Ritten Calendar APIThe calendar API from Ritten — 2 operation(s) for calendar.49.7University of Warsaw Calendar APIAcademic calendar events48.6KolayIK Calendar APIThe Calendar API from KolayIK — 5 operation(s) for calendar.48.3Nittei Scheduler APINittei is MeetsMore's self-hosted calendar and scheduler server, written in Rust (Axum + SQLx + PostgreSQL)...47.8Purdue Events Calendar API (Localist tenant)Purdue's public events calendar at events.purdue.edu serves a live JSON events API on the Localist v2 contr...46.8Google Calendar Calendars APIThe Calendars API from Google Calendar — 6 operation(s) for calendars.46.3airbnb Calendar APIOperations for managing listing availability, pricing, and calendar synchronization across platforms.45.9TreasurySpring Calendar APIGet Calendar information45.9Kumospace Calendar APIThe Calendar API from Kumospace — 7 operation(s) for calendar.45.2Microsoft Project Calendars APIManage enterprise calendars45.1CCP Games Calendar APIThe Calendar API from CCP Games — 3 operation(s) for calendar.43.4EVE Online Calendar APIThe Calendar API from EVE Online — 6 operation(s) for calendar.43.4GuestReady Calendar APIThe calendar API from GuestReady — 2 operation(s) for calendar.43.4Indian Institute of Technology Bombay Calendar APIThe calendar API from Indian Institute of Technology Bombay — 11 operation(s) for calendar.42.5Reclaim.ai Calendars APIThe calendars API from Reclaim.ai — 20 operation(s) for calendars.42.4CrunchDAO Calendar APIThe calendar API from CrunchDAO — 2 operation(s) for calendar.41.4Aiera Calendar APIThe Calendar API from Aiera — 3 operation(s) for calendar.40.9Magic Moment Calendars APIThe calendars API from Magic Moment — 4 operation(s) for calendars.40.0UF Events Calendar (LiveWhale tenancy)The UF events calendar runs on LiveWhale Calendar. calendar.ufl.edu CNAMEs to ufl-prod.lwcal.com — again a ...39.8Reonic Calendars APIReonic-hosted calendars only. External calendar integrations (Google, Microsoft) are visible inside the Reo...39.6Shanghai Jiao Tong University Calendar APICalendar event synchronisation into the campus calendar.39.4
Thin 23 Limited public surface area
Bitrix24 Calendar APIThe Calendar API from Bitrix24 — 21 operation(s) for calendar.38.7Bitrix24 REST APITenant-scoped REST API for managing CRM entities, deals, leads, tasks, calendars, telephony, disk files, us...38.7Xignite Earnings Calendar APICompany earnings announcement dates and earnings calendar data from the earningscalendar.xignite.com service.38.6Xignite Global Holidays APIExchange trading hours, market holidays, and calendar data for global exchanges from the globalholidays.xig...38.6EPFL Memento Events APIEPFL's public events and agenda API, serving the Memento calendar — events, mementos, registrations, domain...38.2Fountain Hire API v2REST API for the Fountain Hire product, covering applicants (create, retrieve, update, delete, list, latest...38.1Microsoft 365 Calendar APIThe Calendar API from Microsoft 365 — 1 operation(s) for calendar.38.0Microsoft Graph APIUnified REST API providing a single endpoint to access data and intelligence across Microsoft 365, Microsof...38.0Planning Center Calendar APIChurch calendaring, events, and facility resources.38.0Luma Calendars APIThe Calendars API from Luma — 25 operation(s) for calendars.37.5Cronofy Calendars APIConnected calendars, application calendars, and account identity.37.0Cal.com Calendars APIThe Calendars API from Cal.com — 9 operation(s) for calendars.36.9Cal.com REST API v2REST API providing full programmatic control over Cal.com resources including calendars, event types, booki...36.9Cornell Events Calendar API (Localist) — tenantThe Cornell events calendar at events.cornell.edu answers a live JSON API at /api/2/events, and the data is...36.9D2L Brightspace Calendar APICourse calendar events.36.0Hospitable Calendar APINightly availability, pricing, and restrictions per property.35.0PetExec Calendar APICompany-wide and per-owner reservation calendars by date range.34.3Guesty Calendars APIListing availability and pricing33.6TableCheck Calendar APIThe calendar API from TableCheck — 1 operation(s) for calendar.32.5Uplisting Calendar APIAvailability, prices, and restrictions per property and date.32.0Webex Hybrid Services APIManage Webex Hybrid Calendar, Hybrid Call Service, Hybrid Message, Video Mesh nodes, and other connectors t...30.9Vetspire Schedule & Appointments APIGraphQL operations over the Schedule domain - list appointments for a location and date range, read provide...29.1Acuity Scheduling REST API v1REST API for managing appointments, appointment types, clients, calendars, availability, intake forms, prod...28.5
Emerging 6 Early or largely undocumented
EDI Central Bank Calendar APICentral bank meeting and announcement calendar via the GetLatestCentralBankCalendar endpoint.26.1EDI Economic Calendar APIForward-looking economic calendar events via the GetLatestEconomicCalendar endpoint.26.1GroupWise Web Services (SOAP)Server-side SOAP protocol for reading and writing a GroupWise user's mailbox, spoken directly to the GroupW...25.3Norish Recipe APIThe HTTP API each Norish instance serves under /api/v1, covering a public health check plus authenticated r...24.5Dentrix Appointments & Scheduling APIRead the schedule and book, reschedule, or cancel appointments. In the Dentrix Developer Program this maps ...19.5HireVue Coordinate (Scheduling) APIAutomated interview scheduling and coordination across candidate and interviewer calendars. Supports self-s...16.8
Minimal 16 Almost no public developer surface
CEPS Events ListingsCEPS maintains a public calendar of policy events, conferences, task force meetings, roundtables and webina...10.0LEAP Calendar APIModeled calendar/diary and appointment-scheduling surface, evidenced by production Marketplace scheduling i...9.1Hebrew CalendarConvert between Gregorian and Hebrew, fetch Shabbat and Holiday times, etc6.0UK Bank HolidaysBank holidays in England and Wales, Scotland and Northern Ireland6.0Church CalendarCatholic liturgical calendar5.1LectServeProtestant liturgical calendar5.1Nager.DatePublic holidays for more than 90 countries5.1Namedays CalendarProvides namedays for multiple countries5.1Non-Working DaysSimple REST API for checking working, non-working or short days for Russia, CIS, USA and other5.1Public HolidaysData on national, regional, and religious holidays via API5.1Festivo Public HolidaysFastest and most advanced public holiday and observance service on the market4.6Examity Appointments (Scheduling) APICreate, reschedule, and cancel proctoring appointments for a test-taker against a registered exam, and quer...4.3Czech Namedays CalendarLookup for a name and returns nameday date4.1Non-Working DaysDatabase of ICS files for non working days3.5Russian CalendarCheck if a date is a Russian holiday or not3.5Clockwise REST APIREST API for the Clockwise AI calendar optimization platform, providing programmatic access to focus time m...0.0

Companies reaching this through an API (68)

These companies publish an API, specification or operation carrying “Calendar” but do not classify their business under it. Listed unranked and kept out of the count above, because one tagged operation is not a statement about what a company does.

ActiveCampaign Aiera Airbnb Alpaca AlphaAI APIVerve Bentley Systems Bitrix24 Blue Prism CCP Games CEPS (Centre for European Policy Studies) Charthop Cisco Collaboration Hybrid Solutions Cisco XDR Clear Street Clio Cornell University CrunchDAO D2L Brightspace Dentrix EODHD EPFL EVE Online Everbridge Examity Exchange Data International Fountain Google GuestReady Guesty HighLevel HireVue Hospitable Hostaway Indian Institute of Technology Bombay KISI KolayIK Kumospace LEAP Magic Moment Microsoft Microsoft Office Microsoft Office 365 Microsoft Project Novell PetExec Planning Center Purdue University Reonic Ritten
Show all 68 companies ↓
SAP BI Tools Shanghai Jiao Tong University SIX TableCheck ThetaData Trakt TreasurySpring Unified.to University of Florida University of Warsaw Uplisting VaultRE Vetspire Wispr Flow Xignite ZnanyLekarz Zoho Zoom

Score breakdown

Frequency
64.9
log-scaled weighted occurrences
Breadth
1.4
spread across providers
Quality lift
33.0
mean composite of providers using it
Cohesion
11.9
strength of nearest seed neighbor

Related tags

Scheduling 40 co-occurrences Meetings 20 co-occurrences Mail 12 co-occurrences Productivity 26 co-occurrences Appointments 13 co-occurrences Availability 11 co-occurrences Holidays 7 co-occurrences Contacts 21 co-occurrences

Where this tag comes from

Provider tag53
Api tag101
Openapi tag50
Openapi op tag218

Cohort brief

Auto-generated

The 48 providers in the APIs.io catalog tagged Calendar, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers
48
all scored
Mean Kin Score
29.3
+6.4 vs catalog 22.9
Mean Agent Readiness
17.1
+5.2 vs catalog 11.9
Spread
0–93.2
median 28 · σ 22.5
How the 48 split by band
Exemplar 2Strong 6Developing 8Thin 10Emerging 7Minimal 15
Facet averages, against the whole catalog
FacetThis cohortCatalogDifferenceScored
Contract Quality 29 17.6 +11.4 48
Access Clarity 34.4 26.5 +7.9 48
Developer Ergonomics 28.3 23.2 +5.1 48
Operational Transparency 18 13.7 +4.3 48
Contract Governance 8.3 6.3 +2 48
Discoverability 57.5 58.1 -0.6 48

A facet is averaged over the members that carry it, not over the whole cohort — the “Scored” column is that count. Averaging an absent facet as zero would score our own coverage gaps as the providers’ posture.

What this cohort publishes
ArtifactThis cohortCatalogDifference
MCP server (any) 21% 14% +7
MCP server (first-party) 21% 12% +9
Agent Skills 0% 0% 0
OAuth scopes 15% 11% +4
Security 100% 98% +2
Arazzo workflows 8% 2% +6
Governance rules 31% 14% +17

mcp_pct counts any mcp/ artifact including ones API Evangelist derived from the provider OpenAPI; mcp_first_party_pct counts only servers the provider publishes. Prefer the latter.

Top by Kin Score
  1. 1 Nylas 93.2
  2. 2 CycleCalcs 67
  3. 3 Chili Piper 66
  4. 4 Microsoft Outlook 66
  5. 5 Google Workspace 60.5
  6. 6 Microsoft Exchange 58.3
  7. 7 Amazon WorkMail 57.1
  8. 8 Calendarific 54.3
  9. 9 Checkiday - National Holiday and Event API 52.1
  10. 10 MeetsMore 47.8
Top by Agent Readiness
  1. 1 Nylas 56.6
  2. 2 Chili Piper 55.6
  3. 3 CycleCalcs 49.4
  4. 4 SavvyCal 48.8
  5. 5 Cal.com 48
  6. 6 Microsoft Outlook 47.5
  7. 7 Luma 44.5
  8. 8 Calendly 43.1
  9. 9 Calendarific 31
  10. 10 Microsoft Exchange 30.9
All 53 members of this roster resolve to a scored provider in the catalog.Generated from the catalog build of 5 October 2026, across 29093 providers, using the same computation served by the APIs.io cohort API. Briefs are published for rosters of 5 or more scored providers; below that a distribution is not meaningful.

Work with this as data

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MCP server

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https://apis.io/mcp

Tools for tags

7 MCP tools reach this
  • find_tagsBrowse and filter every tag in the catalog.
  • get_cohortThis tag as a scored cohort — every provider carrying it, with scores.
  • cohort_statsPRO — the distribution across this tag: mean, median, band split, adoption rates.
  • cohort_rankingsPRO — the leaderboard, on composite AND agent-readiness axes.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

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This tag 
curl "https://apis.io/api/v1/tags/calendar"
All tags 
curl "https://apis.io/api/v1/tags?limit=25"
As a scored cohort 
curl "https://apis.io/api/v1/cohorts/tag/calendar"
The distribution (Pro) 
curl "https://apis.io/api/v1/cohorts/tag/calendar/stats" \
  -H "X-API-Key: $APIS_IO_KEY"

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