The university I went to had a 4D hypercube in the lobby. (Or a shadow of one, anyway)

My two cents:

When dealing with four dimensions, time can be considered a dimension. After all, what is a dimension, anyway? A dimension (expressed mathematically) is simply another independent variable in an equation. For example, a "four dimensional" equation (cube, sphere, or otherwise) is simply an equation that takes four separate pieces of data to establish a complete set. Those pieces of data could be dogs, cats, pigs, and pink bunnies, and the equation would represent varying amounts of each independent variable.

In the universe around us, we say that there are three "real" dimensions because these are the ones that we percieve. You can map any point in space to a three dimensional set. The reason that physicists say that time is the fourth dimension is that an extra piece of information is required if you want to know when the thing will be there. After all, nothing in this universe is completely static, so in the dynamic universe we live in, the time element is helpful. Keep in mind that mapping time to the fourth dimension is a helpful mathematical construct and nothing more. Speculating about the nature of time will not change this.

Also, just a little bit of extra info, according to Richard Feynman and Quantum Electrodynamics, an anti-particle is one that moves backwards in time. So it would appear that time must be a two-way phenomenon. My two cents turned out to be more like ten.