There is no scientific research behind the assertion that the end of the world as we know it will take place on a Monday. But I will tell you why I think it will.
Monday: the second day of the week; first day of the working week (the dictionary). Ok the definition has nothing to do with this but I think Monday feels more like the first day of the week. Also, which day of the week Monday falls has nothing to do with anything as well. Monday is like all the rest of the days. If you awoke from a coma and someone told you it was Monday, you may think to yourself "What difference does it make? I was in a coma. It feels more like a Tuesday anyway." On to the point. I chose Monday arbitrarily. There is no method. Monday just seems to be the most dreaded day of the week. Then again, I don't think anyone will be thinking "Damn, it had to happen on a Monday, why couldn't it have happened on a Wednesday?"
Ok let me offer one reason other than a stab in the dark as to why Monday is my choice... Bad stock market news comes out on Fridays after the markets are closed. When Monday comes, people will panic causing chaos in the market and on the streets (namely at the banks).
Monday is just as good as any other day for an apocalypse commencement. This prophecy thing is easy.