From Lisa Chiu, former About.com Guide [extracted]
The seventh day of the seventh month of the lunar calendar is known as Qi Xi Jie, a traditional holiday that has been recently called China’s Valentine’s Day.
The story goes that the the two fell in love and got married, but their bond was met with disapproval by Wangmu, Zhinu’s mother and the queen of heaven. Niulang is viewed as the star Altair and Zhinu as the star Vega. With a swift move of her hairpin, she separated the two with a river in the sky, known today as the Milky Way.
But the queen took pity on them and gave them one night of the year to spend together. On Qi Xi Jie, the queen is said to send magpies to bridge the celestial gap between the two star lovers.
Many Chinese view it as another chance to buy gifts for their sweethearts, and the holiday is repeated again on February 14, where Valentine’s culture appears to have permeated the earth.