April is Yom Hashoah, or Holocaust Remembrance Day, and marks the start of a week's worth of National Days of Remembrance.
...[s]ince the early 1960s, the sound of a siren on Yom Hashoah stops traffic and pedestrians throughout the State of Israel for two minutes of silent devotion. The siren blows at sundown and once again at 11:00 A.M. on this date. All radio and television programs during this day are connected in one way or another with the Jewish destiny in World War II, including personal interviews with survivors. Even the musical programs are adapted to the atmosphere of Yom Hashoah. There is no public entertainment on Yom Hashoah, as theaters, cinemas, pubs, and other public venues are closed throughout Israel.
In North America,
Jews ... observe Yom Hashoah within the synagogue as well as in the broader Jewish community. Commemorations range from synagogue services to communal vigils and educational programs. A few congregations find it more practical to hold commemorative ceremonies on the closest Sunday to Yom Hashoah. Many Yom Hashoah programs feature a talk by a Holocaust survivor, recitation of appropriate songs and readings, or viewing of a Holocaust-themed film. Some communities choose to emphasize the depth of loss that Jews experienced in the Holocaust by reading the names of Holocaust victims one after another--dramatizing the unfathomable notion of six million deaths.
Some resources for reflection and prayer: