On January 26 1938, Aboriginal leaders including William Cooper, met for a Day of Mourning, seeking equality and full citizenship (though it would take another 30 years).

The Australian Churches were then asked to set aside the Sunday before January 26 as Aboriginal Sunday (previously called Aborigines' Day), a day for Christians to act in solidarity with Aboriginal peoples and the injustices being experienced.

The first Aboriginal Sunday is suggested as occurring in 1941, although was referenced in a letter from William Cooper to the John McEwen, Minister for the Interior written on 19 January 1938 and also referenced in the Herald (Melbourne) newspaper on 18 January 1939.

Today, the Common Grace movement encourages individual congregations to reclaim William Cooper’s Aboriginal Sunday and each year provides a free Church Resource Toolkit developed by Aboriginal Christian Leaders to equip churches and faith communities to act in solidarity with Aboriginal peoples on the Sunday directly before January 26.