"He continues to respond positively to treatment and we are encouraged by the progress he is making," President Jacob Zuma said after visiting Mandela. A statement from Zuma's office said Mandela was steadily improving.
"We are proud to call this international icon our own as South Africans and wish him good health," Zuma said in the statement. He thanked South Africans for supporting Mandela during his hospitalization with "undying love and compassion" and responding to a call to give the beloved figure "the biggest birthday celebration ever this year."
The anti-apartheid leader was taken to a Pretoria hospital on June 8 for treatment for a recurring lung infection. In previous announcements, the government said he was in critical but stable condition. Court documents filed by Mandela's family earlier this month had said Mandela was on life support.
Mandela is making "remarkable progress," said one of his daughters, Zindzi, on Thursday, after tense weeks in which some South Africans talked about the possibility that Mandela was on the verge of dying.
"We look forward to having him back at home soon," the South African Press Association quoted Zindzi Mandela as saying during the government rollout of a digital ID card system.
Ndileka Mandela, a granddaughter of Mandela, poured soup for poor children at a charity event and said her family had been unsure about whether her grandfather would live to see his birthday.
"But because of the fighter that he is, he was able to fight a repressive system, and he was able, through God and everybody's prayers, to make it today," she said.
Thursday also marked the 15th wedding anniversary of Mandela and Graca Machel, the former First Lady of Mozambique who has spent much of the time at her husband's side during his illness.
Many South Africans volunteered 67 minutes for charity to match what organizers said were the 67 years of public service by Mandela, leader of the fight against white minority rule.
"We don't only recognize him on this day. We put smiles on other people's faces, we donate to other people less fortunate," Thato Williams, a 13-year-old student, said during an assembly in Mandela's honor at Melpark Primary School in Johannesburg. Some 700 students there sang "Happy Birthday" in a hall filled with posters created to honor Mandela's contributions to peace and education.
President Zuma opened low-cost housing for poor black and white families in the Pretoria area. South Africa is struggling with high unemployment, labor unrest, service delivery shortcomings and other social challenges that have dampened the expectations of a better life for black South Africans after the end of apartheid two decades ago.
Retired archbishop Desmond Tutu helped to paint a school outside Cape Town, saying Mandela makes South Africans "walk tall" and urging compatriots to refrain from divisive behavior.
Elsewhere, social workers, military commanders and private company employees others planted trees, cleaned classrooms and donated food, blankets and other basic necessities in poor areas. Doctors administered eye tests, inoculations and other medical treatments.
Visiting Pretoria, European Union President Herman Van Rompuy packed food parcels and said his two sons were fans of Mandela, whom he described as "the brightest sun of South Africa."
The U.N has declared July 18 as Nelson Mandela International Day as a way of recognizing the Nobel Peace Prize winner's contribution to reconciliation. A procession was held in India to honor Mandela. In Washington, U.S. congressional leaders planned a ceremony later Thursday.
Mandela was jailed for 27 years under apartheid and led a difficult transition from apartheid to democracy, becoming president in all-race elections in 1994. He served one five-year term, evolving into a global statesman and pursuing charitable causes after that. He retired from public life years ago.
"South Africa is a better place today than it was in 1994 and this is because of the contribution made by Madiba and his collective," the ruling African National Congress, once led by Mandela, said in a statement.
The ANC was the leading liberation movement during apartheid, and has dominated politics since the end of white rule. However, it has come under increasing criticism because of corruption scandals and frustration over poverty and other problems.
In recent months, the ANC and opposition groups have sought to emphasize their connections to Mandela's legacy in the fight for democracy, leading to accusations of political opportunism on both sides.
F.W. de Klerk, the last president of the apartheid era, said in a statement that Mandela's birthday "should be a time for quiet and respectful contemplation - and not for unseemly squabbling over the ownership of Mr Mandela's heritage."
He continued: "Throughout his life he has been a loyal and stalwart member of the ANC - but I believe that through his example and through his unwavering commitment to national reconciliation - all South Africans, regardless of their race or political affiliation, can now proudly call him their own."
De Klerk shared the Nobel prize with Mandela in 1993 because he effectively negotiated his own government out of power, working on a political transition with Mandela that allayed fears of all-out racial conflict.
Mandela's former wife said she wanted to reassure South Africans who fear the eventual death of Mandela, a unifying figure, would open the way to unrest.
"There are sometimes prophets of doom who say the country will come to a standstill," said Winnie Madikizela-Mandela, herself a prominent figure in the anti-apartheid movement, in an interview with South Africa's Radio 702.
However, she said: "The country will solidify, come together and carry on."
Associated Press writer Wandoo Makurdi contributed to this report from Johannesburg.