FREE — count business days between two dates

Unmetered and unpriced; every country on every brand. business_days counts (from, to] and is negative when to is before from, so add(from, business_days) lands on to whenever to is a business day. business_days_inclusive counts both ends. Also returns weekend days and the public holidays in range. Range at most 1096 calendar days. Refusals are free JSON: 400 for a malformed country, date or n; 404 for an unknown country; 422 year_not_held when a date falls in a year whose holidays we do not h...