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API · /easter-api

Easter & Computus API

healthy 3,657 Subscribers

Computus and calendar maths as an API, computed locally and deterministically. The easter endpoint computes the date of Easter Sunday for any year — both the Western date, by the Anonymous Gregorian (Meeus/Jones/Butcher) algorithm, and the Orthodox date, by the Julian computus converted to the Gregorian calendar — with the month name and weekday; Easter is the first Sunday after the paschal full moon, so 2024 falls on 31 March in the West and 5 May for the Orthodox church, while in 2025 both coincide on 20 April. The movable-feasts endpoint returns the whole Easter-anchored cycle for a year as calendar dates — Ash Wednesday (−46 days), Palm Sunday (−7), Maundy Thursday (−3), Good Friday (−2), Ascension (+39), Pentecost (+49) and Corpus Christi (+60). The julian-day endpoint converts a Gregorian date to its Julian Day Number — the continuous day count astronomers use, where 2451545 is 1 January 2000 — and back, returning the weekday too. Years are in the Gregorian calendar. Everything is computed locally and deterministically, so it is instant and private. Ideal for calendar, scheduling, liturgical, church, holiday-planning and date-arithmetic app developers, movable-feast and Julian-day tools, and almanac software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the computus and Julian-day conversion; for general date arithmetic and time zones use a date-time API.

#easter #computus #movable-feasts #julian-day #calendar #developer-tools
api.oanor.com/easter-api
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Machine-readable spec so AI agents can integrate this API.

/api/easter-api/openapi.json
/api/easter-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
89 ms
Server probes · 24h
Subscribers
3,657
active
Total calls
76
last 7 days
status Full status page → · 12 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 7,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 7,000 calls/month
  • 2 req/sec
  • Western + Orthodox Easter + Julian day
  • No credit card
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Starter

€3.80 /month

  • 70,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • 70,000 calls/month
  • 6 req/sec
  • Movable feasts, weekday, JDN both ways
  • Email support
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Pro

€10.50 /month

  • 310,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • 310,000 calls/month
  • 15 req/sec
  • Calendar-app & almanac pipelines
  • Priority support
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Mega

€34.00 /month

  • 1,650,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,650,000 calls/month
  • 40 req/sec
  • Platform scale
  • Dedicated SLA
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IPO Calendar API

The live pipeline of US stock-market initial public offerings, served from Nasdaq's public IPO calendar — no key, nothing cached. This is the deal flow of companies going public, the data IPO investors and traders watch. The priced endpoint returns the IPOs that have just priced and begun trading, each with the ticker, company, exchange, offer price, shares offered, pricing date and total deal size. The upcoming endpoint returns the IPOs expected to price soon, with their price range and expected date — the near-term pipeline. The filed endpoint returns companies that have newly filed to go public, the earliest signal of a coming listing. The calendar endpoint returns the whole month in one call — priced, upcoming and filed — with counts. Any month back through the archive can be requested, and with no month it returns the current one. Everything is live from Nasdaq, nothing stored. This is the IPO-pipeline layer for any trading, investing, screener or finance app. Distinct from stock-quote and earnings APIs — this is the calendar of companies coming to market: priced, upcoming and freshly filed offerings. 4 endpoints, no key on our side.

api.oanor.com/ipo-api

Market Calendar API

Live corporate-events calendar for US-listed stocks — the dates that move markets — served straight from Nasdaq's public calendar feed. For any trading day it answers the three questions a trader's calendar needs. The earnings endpoint lists every company reporting on a date with the session (pre-market or after-hours), the consensus EPS forecast, the number of analyst estimates, market cap and the year-ago actual EPS — so you can see, for example, Oracle reporting after the close with a $1.58 consensus against $1.35 a year earlier. The dividends endpoint gives the dividend calendar: the ex-dividend, record and payment dates, the per-share rate and the indicated annual dividend. The splits endpoint gives the stock-split calendar with the split ratio and execution date. This is the forward event-calendar layer every trading, portfolio, screener, earnings-tracker and finance app needs — read live from Nasdaq, nothing cached or stored. Pass any date as YYYY-MM-DD, or omit it for today. Distinct from price, quote and fundamentals APIs — this is the forward calendar of corporate events: who reports, who pays, who splits, and when. 4 endpoints.

api.oanor.com/marketcalendar-api

Recurrence Rule API

Expand and describe RFC 5545 recurrence rules — the RRULE that powers calendar repeats. The expand endpoint takes an RRULE and a start date-time and returns the next occurrence dates, correctly handling FREQ (daily, weekly, monthly, yearly and the finer hourly/minutely/secondly), INTERVAL (every 2 weeks…), COUNT and UNTIL, BYDAY including ordinals like 2MO or -1FR (so "the last Friday of the month" or "the third Sunday of June"), BYMONTHDAY including negatives (-1 for the last day of the month), BYMONTH and WKST. The describe endpoint turns a rule into a plain-English sentence such as "every week on Monday, Wednesday and Friday, 10 times". Everything is computed locally in UTC and deterministically, so it is instant, private and identical on every machine. Ideal for scheduling and booking systems, calendar and reminder apps, billing and subscription cycles, job and report scheduling, and showing customers when something next happens. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This expands the recurrence rule; to build a downloadable .ics calendar event use an iCalendar API, and for plain date arithmetic use a date-time API.

api.oanor.com/rrule-api

iCalendar API

Build a valid RFC 5545 iCalendar (.ics) event from simple parameters — and get ready-to-use "add to calendar" links for Google, Outlook, Office 365 and Yahoo. Pass a title, start and end (ISO 8601 or unix timestamps, in UTC) — or a duration in minutes, or an all-day flag — plus optional location, description, URL, organizer, an RRULE recurrence (e.g. FREQ=WEEKLY) and a reminder (a VALARM N minutes before). The service returns the fully-formed .ics text with correct escaping and 75-octet line folding, a base64 data: URI you can drop straight into a download link, and the four calendar deep-links. A second endpoint parses raw .ics text back into structured JSON events. Everything is computed locally with no network calls, so it is fast and deterministic. Built for booking and scheduling flows, event pages, email "add to calendar" buttons, reminders and no-code automations. A calendar-event builder — distinct from date/time math (datetime), public-holiday data (holidays) and the Jewish calendar (hebcal). No upstream key, no cache.

api.oanor.com/ical-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Easter & Computus API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Easter & Computus API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Easter & Computus API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Easter & Computus API cost?
Easter & Computus API has a free tier with 100 calls / month. Paid plans start at €3.80 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Easter & Computus API GDPR-compliant?
All requests to Easter & Computus API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/easter-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/easter-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/easter-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/easter-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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