Holiday API reference

Base URL https://duedateapi.com. Use your DueDate API key: Authorization: Bearer YOUR_API_KEY or x-api-key. Each call counts as one API call on your plan's monthly quota (Free: 1,000 a month). Errors are JSON {"error":{"code","message"}}: 401 missing or invalid key, 429 quota reached, 400 bad input. Responses are wrapped in {"data": …}, like the rest of DueDate.

Endpoint	Parameters
`GET /v1/holidays/list`	country (required), year (default: current year), region, type (public, bank, optional, observance… per country)
`GET /v1/holidays/is-business-day`	country, date (YYYY-MM-DD), region
`GET /v1/holidays/next-business-day`	country, date, region, days (1–365, default 1)
`GET /v1/holidays/countries`	no key needed; lists countries, regions, categories and weekend days

Examples

curl 'https://duedateapi.com/v1/holidays/list?country=GB&year=2027' \
  -H 'Authorization: Bearer YOUR_API_KEY'

curl 'https://duedateapi.com/v1/holidays/is-business-day?country=GB&date=2027-12-27' -H 'Authorization: Bearer YOUR_API_KEY'
curl 'https://duedateapi.com/v1/holidays/next-business-day?country=US&region=CA&date=2026-12-24&days=3' -H 'Authorization: Bearer YOUR_API_KEY'

Business day = not the country's weekend and not a public holiday nationally or in the given region. The older /v1/holidays and /v1/is-business-day endpoints of the due-date API are unchanged.

Data may change; verify critical dates. Holidays come from the open-source python-holidays project. Lunar and Islamic holidays are calculated estimates, and governments can add or move holidays by announcement. Not legal or payroll advice.