Sorry Day is the day set aside to encourage reconciliation between indigenous and non-indigenous Australians, and to draw attention to the situation of the Stolen Generations.
The Stolen Generations are the Aboriginal children taken from their parents to be raised in foster homes and institutions between the late 19th century and the late 1960s.
Audrey Kinnear is co-chair of Australia's National Sorry Day committee and a member of the Stolen Generations.
She says she does not believe the prime minister, John Howard, will ever formally aplogise for the policy but she believes subsequent governments will.
"It will come, but I hope it's sooner rather than later, because a lot of the generation before us would have passed on before they even heard the word. And it is something that came out of testimonies in the national inquiry into the Stolen Generations, that a majority of families wanted an apology from the nation for the harm that they had done, to their families and the whole of the Aboriginal race."
In Canberra, the Great Hall of Parliament was the scene of addresses by former Prime Minister, Malcolm Fraser, and Doris Pilkington, the author of a well-known book about the Stolen Generations called "Rabbit Proof Fence", which was recently made into a movie.
A Ngunnawal woman, Agnes O'shae, told the Canberra audience that Sorry Day remains a vital part of the reconciliation process.
Mrs O'shae says indigenous Australians cannot move on until all non-indigenous Australians acknowledge the misery of the past and apologise.
"Many white Australians may still say, 'We weren't there at the time. We are not responsible for what our forefathers did. Why should we apologise for something we had no control over?' Let me respond. We accept that the people who carried out these policies and practices may have thought they were acting in the best interest of Aboriginal people. What they did, nevertheless, was harmful and wrong."
Democrats' Senator Aden Ridgeway, himself an indigenous Australian, says while he accepts the symbolism of a national apology will have to wait for a change of government, the day-to-day problems facing Aboriginal people cannot.
"People are still waiting for that almighty symbolism of the government being able to step forward and give some national apology. We know that that is not going to happen in the life of this governmnet but I think at the same time, calls can be made about the need to address the problems that exist for the stolen generation members. And also to deal with problems like health and housing and unemployment in our communities."
In Sydney, one of the main events is an organised evening of stories, songs and poetry by members of the Stolen Generations.
In Melbourne, about 300 people marched to the steps of Parliament House, where they heard songs and speechs about indigenous Australians' experiences of being removed from their families.
One indigenous activist, Robbie Thorpe, compared the British arrival in Australia to the recent war in Iraq.
"Captain James Cook put his British flag on our land and claimed it for the British crown. That's an act of war, an act of aggression and war. And they also say that what came of Captain Cook, was Joseph Banks, the man who supposedly delivered smallpox. Smallpox is a weapon of mass destruction. These are the things they did to Aboriginal people in the 18th century. A pre-emptive strike with a weapon of mass destruction."
Sorry Day is being marked in South Australia with a small tent city in the heart of Adelaide's Victoria Square.
The structures are symbolic of the missions and homes that housed members of the Stolen Generations.
Marches have also been organised for Perth and Brisbane.