When was the first stage of girls' generation?

They actually have two debut dates/performances.
1. 2007 August 2nd
This was the date of their 'unofficial' first performance. They performed on the Mnet School of Rock (you could watch a documentary that shows how they prepared for this stage: called Mnet Girls Go To School)

2. 2007 August 5th
This was the date of their 'official' first performance. They performed on SBS Inkigayo (see related link below for video).

So I guess their 'first' stage was August 2nd, but I think their official 'debut' date is August 5th :p