Yom HaShoah is the Hebrew name for Holocaust Remembrance Day. It is held primarily in Israel, but probably observed to some extent by Jews all over the world. Yom HaShoah is today. It began as sundown last night and will end at sundown tonight*.
This video shows what happens in Israel when the Yom HaShoah siren goes off, as the population of Israel remembers the 6 million Jewish people, amongst others, who were ruthlessly and brutally killed in the European Holocaust.
*In the Jewish calendar, a day is counted from when the sun sets to when it sets the following evening.