There are a lot of intricacies in determining the upakarma. Each sect gives importance to one key aspect and determines the day accordingly. One should not forget that there are reputed traditional scholars still alive in each of these sects.Accordingly,one major sect of vipras in Tamil Nadu including us are observing yajur upAkarma on 1st August 2012. We cannot say that it has to be only performed on 2nd August,2012.
Similar is the case with reference to determination of ekAdaSi, SrI KrshNa jayanti, SrI RAma navami , amavAsyA and so on. All these would have regional / sectoral variants. That is the beauty of sanAtana dharma. Starting from Vedas, smrtis, dharma SAstras, sUtras, there are a lot of variations which are there from time immemorial. No one can ever make them uniform all across.
In the light of the above, in these matters the best way is to follow one's own tradition without adversely commenting upon others' traditions and practices. After all, doing upakarma with SraddhA on any of these acceptable days is better than arguing endlessly as if upakarma is being performed by the vipras for the first time ever in BhArata deSa.