I have heard this crap so many times. What they didn't tell me is that the whole religion started, back in 1872, on the premises that Armageddon was coming in 1874. Then, when 1875 came, they pushed the date back to 1878. Then 1914. Then all those other dates, most notably to most of us being 1975.
Now, it is close. It is getting closer. But, for those of you who managed to learn your freshman algebra without being too tired from those late-ending boasting sessions, it is mathematically possible for something to be very close, and forever getting closer without actually getting here. It is called simultaneous equations, and any point where the two intersect is called a "root". Some pairs of equations have one root. Some have multiple roots, as the graphs keep curving while they weave in and out. And others have no roots, as they never intersect. Of these, some have no roots simply because they are closed curves with no intersection. Some will get closer for a time, only to get farther away. And others have no root because they infinitely get closer without actually intersecting.
A prime example of two simultaneous equations with no roots is (Y=1/X; Y=0). Anyone that can plot these on graph paper, or that has the use of a graphics calculator along with the knowledge on how to use it, can try various values for X. As X gets bigger, Y gets closer to the second equation (where Y is zero). However, the two never intersect because X has to be infinity in order to have Y=0 in the first equation. Y always equals 0 in the second. This is a prime example of where something is close, getting closer, and never arrives.
Anyone with this simple understanding of algebraic equations should be able to tell how it is possible for Armageddon to be close, getting closer, yet never arrive. For Armageddon to come into the present, you need the present and Armageddon to have a root (at which point, it comes). If there is no root, you will never see Armageddon. And, something tells me that 2012 is no more going to be the root of this pair (meaning, when Armageddon gets here) than 1874 was.