The Derry Flag flies at half mast on Christmas Eve, with the city celebrating its 100th anniversary.
Dublin city council will celebrate its centenary on December 26 with a flag that pays tribute to the 1916 Rising and the 1916 Easter Rising.
The flag features a Derry motif with a large blue field with the word DERRY in white letters, with a star at the top and a cross.
Dubliners city council was given the responsibility of creating the flag in 1919.
It was given to the city from the Dáil by the Sinn Féin TD, John Redmond, after he was defeated in the 1916 Battle of the Somme.
The new flag has the DERTY design and the words DERY (derry) written in red and blue.
The Irish Republican Army was formed in 1916 and the rebellion was supported by the British government.
The Derry Rising was the largest civil war in Northern Ireland, with over 6,000 soldiers and civilians killed and over 1,000 wounded.
The Rising, which took place on Easter Sunday 1916, saw the Republican Army seize power in Derry, a city of 1.4 million.
Dubliner was the first city in Northern Irish history to have a Catholic-majority council.
The city was first designated a Catholic city in 1894 and in 1917 the first Catholic church was built in the city.
In the 1930s, the city was divided into Protestant and Catholic areas and became known as the Protestant North.
Dubline became a separate city in 1962.
The Protestant population is now estimated at around 10,000.
Dublins most famous resident is the late comedian Eddie Izzard.
Izzard died aged 77 on January 7 this year.