'Bout Hardware release history.

Hey! I'm a new user of Arduino, habe been using it this last semester and I think I'm going to be using it for my degree Project. I have one small problem tough, one of the requisites of the Thesis of the project is to make a timeline of the hardware/software in use. I found release dates of the Arduino IDE, but I can't find the release dates of the Arduino boards, Does somebody know where to find them? I am particularly intrested in the UNO and MEGA boards.

Thanks in advice!