Namedays Calendar vs Nager.Date
Nager.Date is a free, open-source public holiday API covering 204 countries, with endpoints for a year's full holiday list, the next public holiday, whether today is a holiday, and country metadata — all keyless JSON with no rate limiting. It's maintained on GitHub by a single developer and is popular as the default holiday backend baked into several scheduling and HR libraries specifically because it needs no signup. The old v3 endpoints are deprecated; the provider will retire them on 31 January 2027, so new integrations should use v4.
Compare →Namedays Calendar vs Non-Working Days
isdayoff.ru answers one narrow question extremely cheaply: for a date or date range, is it a working day, a weekend, or an official non-working holiday. Responses are bare digit strings (0/1 per day, or 2 for a shortened day) rather than JSON, which keeps payloads tiny for the batch/range endpoint. It documents Russia, Belarus, Ukraine, Kazakhstan, and the US as supported country codes, but live probes this run found only Russia (the default), Belarus, and Kazakhstan return genuinely varying data — the Ukraine and US codes are accepted (HTTP 200) but answered every single day of several different months with a flat, undifferentiated "0". It's free, keyless, and has no published rate limit, built for production-calendar bookkeeping rather than general holiday metadata.
Compare →Namedays Calendar vs UK Bank Holidays
The UK government publishes England & Wales, Scotland, and Northern Ireland bank holidays as a single static JSON file at gov.uk, listing each holiday's date, title, and whether it's a “substitute day” moved from a weekend. It's official, authoritative, and requires nothing beyond an HTTP GET — no key, no rate limit, and it's licensed under the Open Government Licence for reuse including commercially.
Compare →Namedays Calendar vs Hebrew Calendar
Hebcal converts between Gregorian and Hebrew dates and computes Shabbat start/end times, holiday dates, Torah readings, and the Daf Yomi study cycle for any location, driven by the same open-source engine (@hebcal/core) that runs the hebcal.com website. Every endpoint is keyless JSON (or RSS/iCal on other routes) under a Creative Commons Attribution 4.0 license, so results can be reused commercially as long as Hebcal is credited. It's rate-limited to keep the free service polite — no more than 90 requests per 10-second window — and the once-http-only backend now serves over HTTPS as well.
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