When was Pakistan formally admitted to the Shanghai Cooperation Organization?

When was Pakistan formally admitted to the Shanghai Cooperation Organization?

پاکستان کو باضابطہ طور پر شنگھائی تعاون تنظیم میں کب شامل کیا گیا؟
Explanation

On 9 June, 2017 India and Pakistan became full members of the Shanghai Cooperation Organization (SCO).