On what date did the Soviet Union notify Japan that it was declaring war in 1945?

The Soviet Union notified Japan that it was declaring war on August 8, 1945.

Soviet Foreign Minister Vyacheslav Molotov delivered the declaration to Japanese ambassador Naotake Satō in Moscow on the evening of August 8. The Soviet government stated that it would regard itself as at war with Japan from August 9, reflecting the time difference and the planned start of military operations.

Soviet forces began invading Manchuria just after midnight on August 9 in the region’s local time. The offensive targeted the Japanese Kwantung Army and rapidly expanded across Japanese-occupied territory. This invasion fulfilled the Soviet commitment made at the Yalta Conference to enter the war against Japan.

The date can be confused with August 9 because the invasion began that day and the Soviet government’s war status took effect from then. August 8 is the date of the diplomatic notification; August 9 is the date associated with the opening of the invasion.