API

Everything the site runs on is a static JSON file served with Access-Control-Allow-Origin: *. No key, no rate limit, no signup. Cache it — it changes when the dataset is rebuilt, roughly weekly.

Endpoints

Answering “can I post on this date?”

There is no query endpoint on purpose — a static file plus five lines of code is faster than a round trip. Pull the two files for a market once and evaluate locally:

const [events, holidays] = await Promise.all([
  fetch("https://badgood.day/api/v1/events.json").then(r => r.json()),
  fetch("https://badgood.day/api/v1/holidays/US.json").then(r => r.json()),
]);

const on = (market, date) =>
  [...events.events, ...holidays]
    .filter(e => e.countries.includes(market))
    .filter(e => e.occurrences.some(o => o.start <= date && date <= (o.end || o.start)));

const signal = e => e.risk !== "green" ? e.risk : e.opportunity ? "good" : "green";
const worst  = ["green", "good", "amber", "red"];

const hits = on("US", "2026-09-11");
const verdict = hits.reduce((a, e) =>
  worst.indexOf(signal(e)) > worst.indexOf(a) ? signal(e) : a, "green");
// => "red"  ·  hits[0].name === "September 11 attacks anniversary (Patriot Day)"

Fields worth knowing

• risk — red · amber · green. Combine with opportunity: true to get the fourth signal.
• occurrences — [{start, end}], ISO dates, inclusive. Multi-day periods are one entry.
• at — exact moments a country stops, as {t, tz, what}. Convert with the IANA zone.
• approx — lunar or moon-sighting date, may shift ±1 day.
• regional / counties — not nationwide.
• greeting — the phrase used in-market on opportunity dates.

Licence

Dataset CC BY-SA 4.0 (it embeds Wikipedia extracts). Attribution: “On This Day — badgood.day”. Public-holiday rows originate from Nager.Date, Hebcal and the Aladhan Hijri calendar; population and religion figures from the CIA World Factbook (public domain).