Holocaust Memorial Day will be marked across the world on Friday with a series of events including services, talks, concerts and vigils remembering not only those who died in the second world war but the victims of many genocides since.
Ceremonies will take place at the headquarters of the United Nations in New York, in Israel and at Auschwitz in Poland. The day is commemorated worldwide every 27 January, the date the Nazi death camp Auschwitz-Birkenau was liberated by Soviet troops in 1945.
In Britain – where the date has been marked annually since 2001 – a survey carried out for the Holocaust Memorial Day Trust shows that more than half the respondents felt social media had a role to play in fighting hatred and discrimination. Although the poll showed social media had largely replaced face-to-face meetings, manybelieved speaking up online could make a real difference.
The survey was carried out to highlight the trust's theme for this year of Speak Up, Speak Out, urging people to speak out against hatred and discrimination: many signed pledges in Trafalgar Square in London on the eve of memorial day.
In a special video message, the Archbishop of Canterbury, Rowan Williams, urged people to find the courage to speak up for the rights of neighbours and strangers, "for people like us and also for people not like us".
"Holocaust Memorial Day brings back to our minds the appalling consequences of a situation when people don't speak for their neighbour and don't speak for the stranger, when people are concerned for their own security, their own comfort zones. And when we look back on that tragic history, one of the things that prevents it from being a totally dark night is the presence of some of those who were willing to speak for strangers and to take risks alongside strangers."
The archbishop referred to the example of one of the founders of the Council of Christians and Jews - which recently celebrated its 70th anniversary - Archbishop William Temple, who had "come to the conclusion that he had to learn to speak for the stranger".
In 1943, Temple argued in the House of Lords that the west had to do more to combat the atrocities against Jews under the Nazis. The council had led to decades "of intense friendship and relationship building", he said.
York, whose Jewish citizens were slaughtered in 1190, is launching a Jewish History Trail, and held a prayer ceremony at the grassy mound by Clifford's Tower, the site of the massacre.
In Newport, South Wales, 94-year-old Ron Jones will attend a ceremony at the cathedral, and recall the football matches he played in at the PoW camp attached to the Auschwitz complex. He believes the matches every Sunday helped make him fit enough to survive the long forced marches when the Germans emptied the camp in the final stages of the war.
"It kept us sane, it was a bit of normality, but it sounds wrong somehow to say I've got fond memories of playing football, considering what was going on just over the fence," he told the BBC.
The results of the Holocaust Memorial Trust social media survey were analysed independently by Robin Dunbar, professor of evolutionary anthropology and a fellow of Magdalen College, Oxford, who said: "Our research has shown that people are more prone to saying something on social media that they later regret, because in these digital environments we don't receive the immediate checks and balances that we get during face-to-face interactions. This can therefore result in a careless or inappropriate tweet, or at worst, cyber bullying."
The survey found that 55% of 2,000 people questioned felt social media had replaced face-to-face interaction, and 39% said they had used them to speak up about something they felt passionately about. Of this group, 44% felt what they wrote led to people blogging or tweeting on the issue, or actual changes.
However, 26% admitted they had, or would, say something on a website they would never say face to face. A quarter regretted something they had posted, almost half because they later considered it inappropriate, and 27% because they thought it had upset somebody. More than a third, 36%, said they had witnessed or been a victim of online bullying, and while 41% of this group said they had intervened, almost 25% said they had done nothing.