What is Bank Holiday?

Legal Definition
A bank holiday is a public holiday in the United Kingdom, some Commonwealth countries, other European countries, and a colloquialism for a public holiday in Hong Kong and Ireland. There is no automatic right to time off on these days, although banks close and the majority of the working population is granted time off work or extra pay for working on these days, depending on their contract. The first official bank holidays were the four days named in the Bank Holidays Act 1871, but today the term is colloquially used for Good Friday and Christmas Day which were already public holidays under common law and therefore not official bank holidays in England, Wales and Northern Ireland.
-- Wikipedia
Legal Definition
A date considered a holiday when institutions are expected to be closed.