Today, April 5th, is the first day of the Pure and Bright (in
Mandarin, qīngmíng) solar term.
清明
Pure and Bright might describe the weather as spring takes hold; or at least, what we hope for at this time of the year. It is also the name of one of the most important festivals of the Chinese year, sometimes called in English Tomb Sweeping Day, because that is what people traditionally do on this occasion. This is also a big day for burning paper money by the graves, in order to send it to the spirits of the ancestors. Filial piety being of huge importance in Chinese culture, these offerings to ancestors are a way to continue filial piety beyond the lifespan of one's parents.
Most major Chinese festivals have a set date on the calendar: the fifth day of the fifth month for the Dragon Boat Festival, or the seventh day of the seventh month for "Seventh Night" (Qixi, when the Weaver Star crosses the Milky Way to meet the Heavenly Shepherd, whom she is in love with). Qing Ming is unusual because it is takes place 15 days after the spring equinox, so it is a movable feast in the monthly calendar, but a fixed one in relation to the solar terms.
By the way, Qing Ming is actually the middle day of a three day period sometimes mentioned in Chinese poems, the Cold Food Festival. Traditionally, no fires were lit during these three days, so people ate cold food. Legend has that the festival commemorates a Jie Zhitui of the Warring States period, whose prince wanted him to come to court and take a responsibility role. Jie refused and hid on a mountain; the prince ordered fire to be set to the forest to "smoke him out", but Jie chose to die in the fire instead. The prince repented and instituted the three day fire-less period. I am not very convinced by this explanation, which sounds like a rationalization of an even older tradition. It also supports the idea that, if you are feudal prince, you can have your population atone for your errors.
Anyway, the first time I heard of the Qing Ming festival was in conjunction with a famous Song dynasty painting, which depicts the city of Kaifeng during the festival, with wonderful detail of the crowd, the houses and shops, and the boats on the river. This is just a tiny detail to give you a feeling for the style; you should see the entire scroll
here.