Each year on February 23, my mother used to have her own personal "day of mourning." That was the anniversary of the day in 1945 when her hometown, Pforzheim (in southern Germany), was obliterated by an allied bombing attack. That's now been 67 years, and Mom is no longer here to mourn. So perhaps I'll stand in for her.
Mom had a book documenting the attack titled "Der Untergang Einer Stadt" (The Downfall of a City) that she would read and reread, looking at the pictures for hours.