27 January is an official day of remembrance in Germany. What does this day commemorate?

EDITORIAL LEARNING AID

Why is this answer correct?

On 27 January 1945 the Red Army liberated the Auschwitz extermination camp; since 1996 this day has been the official day of remembrance for the victims of National Socialism in Germany. The end of the Second World War is commemorated on 8 May, the Basic Law was promulgated on 23 May 1949, and reunification is celebrated on 3 October.

27 January = liberation of Auschwitz, remembrance of Nazi victims.

This translation and explanation are editorial learning aids. The official German wording and answer key govern the examination.