When is the Chinese Valentine's Day in China?

Qixi Festival  七夕節 or Chinese Valentine's Day
Dates of Chinese Valentine's Day (Qixi Festival) in China time zone:
August 20, 2015;
August 9, 2016;
August 28, 2017;
August 17, 2018;
August 7, 2019
August 25, 2020
Qixi Festival or Double Seven Festival on the 7th day of the 7th lunar month also Girls' Festival  when Cowherd and Weaving maid  牛郎織女|牛郎织女 niu2 lang3 zhi1 nu:3 are allowed their annual meeting.

The festival originated from the romantic legend of two lovers, Zhinü and Niulang, who were the weaver maid and the cowherd, respectively. The tale of The Weaver Girl and the Cowherd has been celebrated in the Qixi Festival since the Han Dynasty. The earliest-known reference to this famous myth dates back to over 2600 years ago, which was told in a poem from the Classic of Poetry. The Qixi festival inspired Tanabatafestival in Japan, Chilseok festival in Korea, and Thất Tịch festival in Vietnam. (Wikipedia)