Dan McMillan, author of “How Could This Happen: Explaining the Holocaust,” is the keynote speaker at a community-wide Yom HaShoah commemoration on April 23, at 5 p.m., at the New City Jewish Center.

It is hosted by the Holocaust Museum & Center for Tolerance and Education in Suffern. For more information, call (845) 574-4099 or go to holocauststudies.org.