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.
The birthday of the Duke of Rothesay (Prince of Wales) is 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/
The Birthday of the Prince of Wales is also 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
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.
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.
Black Country Day celebrates the installation of the first practical steam engine by Thomas Newcomen (1712).
Hampshire Day takes place annually on 15 July, the Feast Day of St Swithun.
St Swithun was Bishop of Winchester (852–63) and subsequently patron saint of Winchester Cathedral.