Even though Germany won during WWII, the current state of Hamlyn Village does not want to remember that, hence the reason why they often claim they won the War.
When Its Celebrated Edit
It is unknown when Victory Day is. It's possible it could be on the 11 November, the day that Germany surrendered during WWI. Though it could also be 10 August, the day when the German occupation of Great Britain ended.
Other "Victories" Edit
The Victory Memorial Camp is the military base in the Garden District, it is there that the home army lads train for WW III. The camp serves as a memorial of the "Victory" that took place in WWI and WWII, when the Germans finally left Britain.
Victory Meat is the name of the local delicacy in Wellington Wells, it is often eaten outside of Victory Day, as there is a great famine in the city. In response to the food shortage, Reg Cutty, the local butcher in St. George's Holm, is the one who distributes V-Meat to the public. It's possible that V-Meat has been in production since the 1950's, though it's only speculatory.
It's also possible that Victory Meat used to contain actual animal food inside a long time ago, and that the current desperate move to keep people from starvation is a recent solution.