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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.

Easter & Computus API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
76 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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api.oanor.com/earnings-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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