Gloucestershire Day was first celebrated in 2020.
Derbyshire Day takes place annually on 22 September.
BBC Radio Derby presenter Andy Whittaker organised a vote, and the chosen date commemorates the first raising of the flag.
Alternative suggestions included: 28 July – Derby, the county town, granted city status; 12 May – the birthday of Florence Nightingale, who spent her early years in the county.
Cumberland Day takes place each year on 24 September.
It marks the anniversary of the baptism of renowned local character John Peel (1776-1854).
Montmouthshire Day takes place each year on 25 September, the feast of Saint Cadoc or Cadog (born c. 497).
Cadoc was the founder of the monastery of Llancarfan, and a pioneer of Celtic Christianity in Wales.
Westmorland Day takes place annually on 29 September.
It marks the date in 1397, when King Richard II created Ralph Neville the first Earl of Westmorland.
A poll at the Westmorland County Show (2013) chose this day.
Other options included: 30 January – birth of Lady Anne Clifford; 30 July – death of Thomas de Strickland; 1 October – battle of Tinghai; 21 October – death of Earl Ralph Neville; 18 December – battle of Clifton (perhaps the last battle on English soil).
Lincolnshire Day takes place annually on 1 October.
It commemorates the Lincolnshire Rising, which began at Louth on 1 October 1536.
The rebels were protesting against the English Reformation and the Dissolution of the Monasteries.
World Vexillology Day commemorates the debut of Flag Bulletin (October 1961), the world’s first periodical dedicated solely to vexillology.
There is no special flag for this day – just go out and fly flags!
Oxfordshire Day is celebrated on 19 October, the principal feast day of St Frideswide, the patron saint of the city and university of Oxford.
Frideswide (c.650 – 19 October 727) was an English princess and abbess.
She is credited as the founder of a monastery later incorporated into Christ Church, Oxford.
The Virgin Islands celebrate the feast of St Ursula annually on 22 October.
Christopher Columbus named the Virgin Islands in 1493 in honour of St Ursula.
United Nations Day is celebrated annually on 24 October, marking the entry into force of the UN Charter (1945).
Neither the UK Government, the Scottish Government nor the Senedd Cymru currently list it as a flag flying day.