Church Calendar vs Non-Working Days

Church Calendar (calapi) serves the daily Roman Catholic liturgical calendar — season, week, feast rank, and liturgical color — for a given date and country-specific calendar variant, in English, Czech, Latin, or Spanish. It's a small keyless JSON API maintained by a Czech developer alongside the printed liturgical calendars he publishes. There's no pricing or account system of any kind; the only quirk is that its real backend still only serves plain HTTP, timing out on HTTPS.

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.