Honestly, because many people think of this number to be associated with Satan, they pretty much use it as a scapegoat for every problem, disaster, etc.  In reality, it's only supposed to be the symbol for Mankind.  In the Christian worldview, I'm sure everyone knows, 7 is God's number, the number of perfection. 7 days in a week, the Tribulation has 7 years to allow the Anti-Christ to have his season, usually the Old Testament sacrifices included 7 when it was a covenant with God. 6 has always represented Mankind when it dealt with Man.  6 represents humans falling short of God's perfection, though at the same time being in His image and likeness.  It was never meant to be a symbol of doom.  Just misunderstanding, overly zealous Christians taking things out of context.  Again.  I swear, they make us look all gloom and doom.  I'm generally a pretty happy camper. :D