In UAE we do it on 15th of Shabaan (not in Ramadan like Kuwait, Qatar and Bahrain). As kids, it was lots of fun. We used to spend all day walking around town in groups (herds more like it) singing and knock on every door. You are bringing floods of memories to me. Dubai was small back then. We do NOT call it Girgian, We call it "Haq Al lailah" which translates to "for the sake of this holy night"
Beside Kuwait, Qatar and UAE, Bahraini kids also do the same. I am not sure about Oman and Eastern Saudi Arabia, If it is important I'll be happy to ask around and find out.
Nothing has to do with religion though.