What is Black Friday in Australia?

Its where one of the worst bush-fires in the world took place. It happened in Victoria, Australia on the 13 January 1939. 20000 km of land was burned. 71 people died. Over several towns were destroyed. Over 1300 homes and 61 sawmills were destroyed, and a total of 3700 buildings were destroyed. It happened because of a heat-wave and it was estimated that over 3/4 of Victoria was damaged by the fire.