Photo taken on December 5 shows students from the First Experimental Primary School of Nanjing Xiaozhuang College mourning victims of the Nanjing Massacre at a mass grave near Hanzhongmen Gate. (CFP Photo)

In 2014, China's top legislature designated December 13 as the national memorial day for the victims of the Nanjing Massacre, which took place when Japanese troops captured the city in 1937.