The Chingming Festival, which translates as 'clean and bright' festival, occurs during the third lunar month, which is either April 4th of 5th in the Western calendar. During this festival, Chinese people clean and sweep the graves of their ancestors.
It is also a common sight everyday in Hong Kong to see 'Burning Shrines' where joss sticks are burned as an offering to ancestors who have passed into the afterlife. This form of ancestor worship is practiced in both Buddhism and Taoism and is an important part of Chinese culture. It is believed that all aspects of your current physical being only exist because of the your ancestors, who took care of you until your were on 'firm footing'. Paying respect in this way is seen as the ultimate homage.