This depends on when you start counting. It existed during the Spring and Autumn Period, but from the Spring and Autumn Period to the Han Dynasty it was called Yelang State, and in the Tang Dynasty it belonged to Juzhou. During the Song Dynasty, Guiyang was called "Guizhou". In the 16th year of the Yuan Dynasty (1279), the Eighth Luodian Xuanwei Division was established. In the 19th year of the Yuan Dynasty (1282), the Military and Civilian Xuanwei Department of Shunyuan and other roads was established. In the 29th year of the Yuan Dynasty (1292), the Shunyuan and Bafan Xuanwei Divisions merged, and the Eighth Shunyuan Xuanwei Division Marshal's Mansion was established in Guiyang. It was still called Guizhou, but the rulers of the Yuan Dynasty called it Shunyuan City. In the 11th year of Yongle in the Ming Dynasty (i.e. 1413), Guizhou and other departments were established to accept the government envoys in Guiyang, and Guizhou officially became the 13th province of the Ming Dynasty. So if we want to talk about the official founding of Guiyang, it should be 1292.

The above information comes from Baidu Encyclopedia