My research into the nature of spin is that spin is not a rotation of length, it is a temporal rotation. When a subatomic particle is "spinning" it is spinning between backward time and forward time. The subatomic particles of electron, proton, positron, and antiproton are half-spin because they spin in only the forward direction of time.
When one takes the time (pun intended) to realize that all physical matter of the entire physical Universe exists only in the present moment, and then realizes that all of this matter has a forward time trajectory, then it makes sense that matter is "spinning" only in the forward time direction.
This also implies strongly that there is a physical manifestation of backward time, but since our physical Universe as we see it is composed of only forward-time particles, we do not witness the backward time direction in the present moment.
This also implies that the temporal dimension is not one of linear time... a physical timeline that extends from a time in the past and goes to a time in the future. The implication is that the true temporal dimension is a frequency of forward-backward time.
Further, subatomic particles have the property of right or left spin, which differentiates between matter and antimatter. The right and left spin should then also be temporal dimensions (as opposed to a length dimension) and the right and left spins would refer to a twist in the forward-backward-time frequency.
As such, there would be two temporal dimensions; right-left-time spin and forward-backward-time spin.
We perceive linear time from the perspective of the present moment simply because all normal physical matter (left spin, forward time) is acting like a time-diode. The appearance of forward linear time is actually caused by a limitation of physical matter, itself, and within a broader five-dimensional coordinate system (space-resonance as opposed to space-time).