Can't change skin & my skin has a bug !

Hello,

I can't change my skin, i'll tryied to change my skin 1 week ago it doesn't work and when i goto websites to check if i'll change it , it doesn't work but the interessing part is that it says that my account was created the 01/01/1970 .. , look : http://minecraft-skin-viewer.com/player/iEphysion , i can't change my skin, my friends can but i know some people who can't too !
I wanted to install this skin that i put on the attachement but it won't work, please help me.