Returns whether a given date is a public holiday in a country, and the holiday's name when it is.
Country codes are ISO 3166-1 alpha-2. Pass subdivision for region-specific holidays. Computed locally.
Date to check, YYYY-MM-DD.
ISO 3166-1 alpha-2 country code (e.g. US, GB, DE).
Optional language code for the localized holiday name.
Optional ISO 3166-2 subdivision code (e.g. CA, NSW).