Wiltshire Day takes place annually on 5 June.
It commemorates the first raising of the Wiltshire Flag at County Hall, Trowbridge (2007).
The Falkland Islands celebrate Liberation Day annually on 14 June.
The date commemorates the liberation of the islands from Argentine military occupation in 1982.
Sussex Day takes place annually on 16 June, the feast of St Richard of Chichester (1197–1253), the patron saint of Sussex.
Also known as Richard de Wych, the saint was bishop of Chichester.
Shetland Day takes place annually on 21 June.
Shetland Islands Council chose this date simply because it it the longest day of the year.
Suffolk Day takes place annually on 21 June.
Former BBC radio presenter Mark Murphy created the event in 2016.
It has since become a staple in the Suffolk calendar, hosted by towns across the county.
The Birthday of the Prince of Wales is listed as a flag flying day by UK government guidance.
The Union Flag is specified.
https://www.gov.uk/guidance/designated-days-for-union-flag-flying
Under his Scottish title (Duke of Rothesay), the Birthday is also listed as a flag flying day by Scottish government guidance.
The Scottish Saltire is specified.
https://www.gov.scot/publications/flag-flying-on-government-buildings/
Mercia Day takes place annually on 22 June, the feast of St Alban.
St Alban is the first recorded British Christian martyr, by tradition beheaded in Verulamium (modern St Albans) during the third or fourth centuries.
The British Virgin Islands celebrate Territory Day annually on 1 July.
On this date in 1956 the islands became a separate British Overseas Territory.
The Isle of Man celebrates Tynwald Day (Manx: Laa Tinvaal) annually on 5 July, unless this date falls on a Saturday or Sunday.
In this case Tynwald Day takes place on the following Monday.