Yunnan is in the 7th East Zone, Beijing time is calculated according to the 8th East Zone, so theoretically there is a time difference.
A difference of one degree of longitude is 4 minutes, Beijing time is based on longitude 120, Kunming is 102 east longitude. 120-102 = 18 (degrees), one degree is 4 minutes, so use 18 x 4 = 72 (minutes), 72 minutes = 1 hour and 12 minutes, so Kunming is 1 hour and 12 minutes behind Beijing time.
But Beijing time is used uniformly throughout China.
Expanded Information
The terrain of Yunnan Province is high in the northwest and low in the southeast, descending step by step from north to south, and it is a mountainous plateau terrain, with the mountainous area accounting for 88.64% of the total area of the province. The terrain is divided into two major terrain areas, east and west, bounded by the Yuanjiang Valley and the broad valley of the southern section of the Yunling Mountains. The eastern part of the province is the East Yunnan and Central Yunnan Plateau, which is part of the Yunnan-Guizhou Plateau, and is characterized by gently rolling low mountains and rounded hills.
The western part of the province is characterized by high mountains and valleys, with steep terrain, forming strange and majestic mountain and glacier landscapes. Yunnan Province spans the Yangtze River, Pearl River, Yuanjiang River, Lancang River, Nujiang River and Daying River, which are the six major water systems. Yunnan's climate is basically subtropical and tropical monsoon climate, northwestern Yunnan is a plateau mountain climate.