Maybe our time traveling is due to momentum, we can only go in one direction because we are unable to reverse our path.

Temporal momentum would be unit equivalent to mass. And how do you suppose we might obtain a source of temporal thrust without violating the law of conservation of mass-energy?

Please demonstrate this unit equivalency.

Last random though. If time is another dimension then shouldn't we be able to measure it in units of length. I always though of time sort of like a flip book. each page being one plank second apart. so what is the distance between the pages. it makes sense to me that all dimensions would have the same minimum length so that one plank meter would be equal to one plank second. so you should be able to convert seconds to meters and vice versa. like I said a random though.

In order to physically measure time with a ruler one would need to be capable of freely moving forward and backward in time. Just like a 2d being would need to be able to move up and down in the third dimension in order to measure some object that has up/down dimension.

Or as this threads largest troll somehow got right: to get the length of the time-like component of a space-time four-vector, multiply it by 'c'.