I have to admit that it took me by surprise. As far as I knew, the only day set aside for remembering the victims of the Holocaust was Yom Hashoah, the date chosen by Israel’s Knesset in 1953. Yom Hashoah is observed on the 27th day of Nisan, which falls in April or May. So why was David Cameron, the British Prime Minister, talking about the Holocaust in January?

I had no idea, when I accessed the YouTube clip of that day’s Prime Minister’s Questions, that it contained any mention of the Holocaust. Every Wednesday when the House of Commons is in session, the Prime Minister spends about half an hour fielding questions, first from the leader of the opposition, and then from assorted backbenchers. I enjoy watching Prime Minister’s Questions on YouTube; it’s a very different atmosphere and style of debate than Americans are accustomed to watching.

Sometimes, before proceeding to the substantive questions, the Prime Minister will briefly take note of a non-partisan subject. Most often, that subject is a tribute to military or law enforcement personnel killed in the line of duty, to Members of the House who have recently passed away, or to milestones involving the Royal Family. On this particular occasion, he invited the House to join him in marking Holocaust Memorial Day.

“It is right,” said the Prime Minister, “that our whole country should stand together to remember the darkest hour of humanity.” He also announced plans to build “a striking national memorial in London to show the importance Britain places on preserving the memory of the Holocaust.” Later in the session, in response to a specific question, he noted that “tragically, the remaining Holocaust survivors are coming to the end of their lives.” Many of them, he continued “are now speaking up in the most moving and powerful way,” so “recording their testimonies, which must be part of our memorial, is absolutely vital.”

I might have attributed this Holocaust memorial in January to British quirkiness, but the next morning’s New York Times showed otherwise. It contained an account of a Holocaust memorial ceremony held at the Israeli embassy in Washington D.C., at which four Americans were honored as Righteous Among the Nations, a designation for non-Jews who saved Jewish lives during the Holocaust. President Obama spoke at the ceremony, the first time that a sitting American President has spoken at the Israeli embassy. In the course of his speech, the president summed up what he took to be the overarching lesson of the Holocaust:

Where are you? Who are you? That’s the question that the Holocaust poses to us. We have to consider even in moments of peril, even when we might fear for our own lives, the fact that none of us are powerless. We always have a choice. And today, for most of us, standing up against intolerance doesn’t require the same risks that those we honor today took. It doesn’t require imprisonment or that we face down the barrel of a gun. It does require us to speak out. It does require us to stand firm. We know that evil can flourish if we stand idly by.

The sentiments expressed by Prime Minister Cameron and President Obama were unexceptionable, but what was the nature of the occasion on which they had been expressed? Had someone abducted Yom Hashoah when I wasn’t looking? I knew that there had been some controversy within the Jewish community, particularly among the chareidim, about the date chosen by the Knesset as Yom Hashoah, but as far as I knew no one had persuaded the Knesset to change it.

The internet is a useful tool for obtaining information if you know what you’re looking for, and it didn’t take long for me to find the answer. Back in 2005, on the 60th anniversary of the liberation of Auschwitz by Allied troops, the United Nations General Assembly adopted a resolution designating January 27 as International Holocaust Remembrance Day. I don’t know how many countries pay much attention, but apparently, the United States and Great Britain are among those that do. This day is not a substitute for Yom Hashoah, which remains the Holocaust memorial day in Israel and among Diaspora Jews. Rather, it provides an opportunity for other countries to memorialize the victims of the Holocaust, thus helping to ensure that the world will not forget — and therefore not repeat — what Prime Minister Cameron rightly called “the darkest hour of humanity.”

Selecting a date on which to memorialize the Holocaust has always been a bit tricky. By its nature, after all, the Holocaust was not a single event but a process that unfolded over the course of years. There’s probably no date on the calendar on which some event connected to the Holocaust did not take place. Deciding on a specific date on which to memorialize the victims unavoidably requires us to think about why we want to memorialize the Holocaust and what lessons we want to draw from it. The date chosen may say more about the memorializers than about the victims.

The Knesset, in 1953, chose the 27th of Nisan as Yom HaShoah in order to highlight the Warsaw Ghetto Uprising, which was the only large-scale Jewish revolt against the Nazis. (Actually, the Uprising broke out during Passover, but since there is no practical way to memorialize it then, the commemoration was moved to a few days after the holiday.) The Uprising was not the typical experience of European Jewry under the Nazis, of course, but emphasizing it answered a pressing need for Israel’s founders. The new State’s survival was obviously dependent on how effectively its people could make the transition from helpless victims to fighters prepared to take Jewish history into their own hands. Today, we take the strength and skill of the Israel Defense Forces for granted, so we often lose sight of how precarious the Jewish state’s existence was in its early years. Focusing on the Warsaw Ghetto’s resistance to the Nazis even in the face of hopeless odds served an obvious national purpose at that point in Jewish history.

That emphasis on resistance is one reason that some chareidim have objected to the Knesset’s choice of date for Yom Hashoah. (There’s also a technical halakhic objection arising out of the limitations on mourning during the month of Nisan.) Some have suggested incorporating Holocaust commemoration into existing fast days, either Tisha b’Av or Asarah be Tevet. Underlying any such proposal is the assumption that the Holocaust is not a qualitatively unique event, but rather a particularly egregious example of the persecution and suffering that Jews have endured throughout their centuries of exile.

Such a proposal is a non-starter as long as some of those who experienced these events first hand remain alive. Once the last survivors are gone, however, world Jewry will need to focus on what makes the Holocaust uniquely worthy of continued attention. Does it teach us something different from the lessons we’ve learned from the painful experiences of the preceding centuries of persecution and suffering, or is its enormity merely the result of modern technology being wielded in service of ancient hatred?

The Holocaust has loomed large in the Jewish psyche in the decades since the war ended. Preserving its memory remains among the most deeply felt and least controversial of Jewish obligations. Realizing that preventing another such atrocity requires the Holocaust to be remembered not only by Jews but by all peoples, many Jews have sought to preserve its memory, using a variety of methods — including museums, memorials and school curricula — to bring Holocaust knowledge to a wider audience. The establishment of International Holocaust Remembrance Day appears to be one facet of that process.

The Jewish determination not to forget the Nazis’ attempt at genocide is summed up by the well-known slogan “Never again”. We sometimes overlook the fact that we use this post-Holocaust slogan in two different contexts. Never again will we allow ourselves to depend on others for the protection of Jewish lives, and never again will we allow the world to stand idly by an attempt of genocide against any people. The former commitment, by its nature, is one that only the Jewish people can fulfill; the latter commitment is one that we cannot fulfill alone. All the museums and monuments in the world will count for nothing if the memory of the Holocaust is preserved only among Jews.

Why was January 27th chosen as International Holocaust Remembrance Day? Those countries that wished to memorialize the Holocaust could have adopted Yom Hashoah, the Holocaust memorial day observed in Israel, but the Warsaw Ghetto Uprising does not resonate among non-Jews as it does among Jews. Not surprisingly, Jews and non-Jews see the Holocaust differently, and the calendar of memorial observances reflects that difference.

It was on January 27, 1945 that Auschwitz, the largest and best known of the Nazi death camps — and the one that has come to symbolize the Nazi regime’s attempted genocide — was liberated by Allied troops. Focusing on that event gives implicit support to the view that the victorious Allies — especially the United States and Britain — were the “good guys.” They fought on the right side of that war and ultimately ended the Holocaust in the only way they could — by winning the war and destroying the Nazi regime.

The reality is a bit more complicated. Britain fought and ultimately defeated the Nazis, at one point standing virtually alone in that fight, but it also closed the gates of Palestine, cutting off one of the few potential escape routes to Jews seeking a refuge from Nazi extermination. The United States likewise closed its borders in the critical pre-war years to all but a handful of Jewish refugees. American military might ultimately provided an indispensable component of victory over the Nazis, but the US only entered the war after it was attacked by Japan. While there is clearly no comparison between the evil of the Nazis and the inadequacies of the Allied response, the Allies were not entirely without moral culpability. By focusing attention on the liberation of Auschwitz (and by extension, the other concentration camps as well), they can hope to evade, or at least dilute, any critical examination of their own countries’ actions during that period.

This choice is part of a process of universalizing — and thus de-Judaizing — the Holocaust. If you listen to or read Prime Minister Cameron’s remarks carefully, you may notice that the word “Jew” (or any derivative thereof) is completely missing. President Obama’s remarks are more inclusive in their focus. He spoke more directly about the continuing rise in anti-Semitism, but if you read his words, it’s hard to avoid concluding that he, like most non-Jews, emphasizes the universal message of the Holocaust over its specifically Jewish message.

So perhaps it makes sense to observe two different days in memory of the victims of the Holocaust, one for observance by Jews and the other for observance by everybody else. Maybe the UN General Assembly, by designating January 27 as International Holocaust Remembrance Day, actually did the right thing. God sometimes works in mysterious ways.