Did time begin at the big bang?

physicists say that time began at the big bang but i disagree, i think time has always been in the universe even before the big bang and as long as the super massive expance of space has existed for. i also think that what we know as the universe the part with al the left overs from the big bang stars galaxys and all matter is probably just one small part of the entire universe and the space that the big bang happen in is just a proportion of something much bigger!