March 31 is known as the Day of Genocide of Azerbaijanis, referring to the tragic events that took place on March 31-April 1, 1918, as well as other tragic events in the 19th and 20th centuries that have brought enormous suffering to the Azerbaijani people. It is estimated that well over 500,000 Azerbaijanis have perished as a result of the Azerbaijani Genocide.
After the proclamation of the Azerbaijani Democratic Republic (ADR) on May 28, 1918, the "March Events" were investigated by the ADR Government. In 1919-1920, and the ADR observed March 31 as a National Day of Mourning.
Azerbaijani people were unable to commemorate the Azerbaijani Genocide during the Soviet years (much like Ukrainians were not able to observe Holodomor, and the Circassians were not able to observe Circassian Genocide).
Observation of March 31 was reestablished only after Azerbaijan regained its independence in the 1990s, to commemorate not just one particular massacre but the policy of genocide against Azerbaijani people carried out since the 19th century and throughout the entire 20th century, with the final act being the Khojaly Massacre of 1992.