When did boxing day become a bank holiday?
In the UK, Boxing Day has been a bank holiday since 1871. When 26 December falls on a Saturday, the public holiday is on the following Monday. If 26 December falls on a Sunday, the public holiday is the following Tuesday. 
When did boxing day become a bank holiday in the UK?
1871
Boxing Day
In Scotland, Boxing Day has been specified as an additional bank holiday since 1974, by Royal Proclamation under the Banking and Financial Dealings Act 1971.
When did boxing day become a bank holiday in Scotland?
1974
Boxing Day
Boxing Day
https://en.wikipedia.org/wiki/Boxing%20Day
In the UK, 26 December (unless it is a Sunday) has been a bank holiday since 1871. When 26 December falls on a Saturday, the associated public holiday is on the following Monday. When 26 December falls on a Sunday, the public holiday is the following Tuesday, Monday being the public holiday associated with Christmas Day.[27]
Boxing Day
In the UK, Boxing Day has been a bank holiday since 1871. When 26 December falls on a Saturday, the associated public holiday is on the following Monday and if 26 December falls on a Sunday, the public holiday is the following Tuesday, Monday being the public holiday associated with Christmas Day. In Scotland, Boxing Day has been specified as an additional bank holiday since 1974, by Royal Proclamation under the Banking and Financial Dealings Act 1971.