The 1995 Srebrenica genocide will in future be marked around the world on July 11, following a vote by United Nations General Assembly in New York on Thursday.
The "International Day of Reflection and Commemoration" for the 8,000 Bosnian Muslims who were massacred was sponsored by Germany and Rwanda but encountered opposition from Serbia and other countries.
The day is to be officially marked from next year, 40 years after the event.
"Our initiative is about honouring the memory of the victims and supporting the survivors who continue to live with the scars of that fateful time," German ambassador Antje Leendertse said.
The resolution condemns without reservation any denial of the Srebrenica genocide as a historical event along with actions glorifying those convicted of war crimes, crimes against humanity and genocide by international courts, including those responsible for the Srebrenica genocide.
The outcome of the vote did not match expectations, with just 84 member countries in favour and 19 against, with 68 abstentions. Virtually all Balkan countries voted in favour.
China, Russia and Hungary joined Serbia in opposing the resolution. The Serbian delegation argued that it would serve to divide the region and establish a hierarchy among the victims of the war.
Ahead of the vote, Serbian President Aleksandar Vučić addressed the assembly. "It is difficult to speak after Germany that stands for the most powerful country in Europe, and which believes that it is unmistakably entitled to give moral lessons to all those who disagree with it," he said.
He asked why Berlin had kept the work on the resolution secret and said it would reopen old wounds and cause chaos in the Balkans. "Why did those people not start speaking about genocide that their country has committed?" Vučić queried in reference to the Holocaust.
Leendertse responded that the resolution was "not directed against anybody – not against Serbia, a valued member of this organization. If at all, it is directed against perpetrators of a genocide," she said.
The Srebrenica massacre took place on July 11, 1995 during the Bosnian War and during subsequent days. Most of the victims were men and boys who had been separated from the group, while women, girls and small children were bused to territory controlled by the Bosnian army.
The Yugoslavia war crimes tribunal (ICTY) and the International Court of Justice (ICJ) have established legally that genocide was perpetrated.
The political head of the Bosnian Serbs at the time, Radovan Karadžić, and Ratko Mladić, the commander of the Bosnian Serb army, were handed life sentences by the ICTY.
Denial of the Srebrenica genocide is virtually state policy in Serbia and in the Serbian part of Bosnia, known as Republika Srpska. The perpetrators are seen by many there as heroes.