The Standing Committee of the National People's Congress, (NPC) ratified September 3 as the victory day and December 13 the national memorial day for victims of the Nanjing massacre by Japanese troops, official media reported.
The victory day will be observed to mark the signing of the instrument of surrender by the Japanese government in 1945.
China's historians assert that over three lakh people were killed in the Nanjing massacre.
"The approval of the national days has great historical significance and is a necessity in current circumstances," said a foreign ministry official.
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"We urge Japanese leaders to face squarely and reflect on Japan's aggression history with a highly responsible attitude toward history, the people and the future, to correct their mistakes and change their course," said the official.
The resolutions were adopted amid a glare of publicity in the official media arousing national sentiments against Japan.
State-run Global Times, in a scathing editorial, said: "Japan's invasion of China was the most humiliating event for the Chinese people. We try to cover up that period of humiliation with heroism, a word that hardly convinces. It is time to face up to the war. We claimed the final victory, but the sacrifice we paid was devastating.
"The Nanjing Massacre may be the most bloody event during WWII where the brutality of Japanese troops and the incompetence of the Chinese government and army formed the sharpest contrast," it said.