Full Idea
The three most significant arrows of time are the Thermodynamic (the direction from order to disorder), the Psychological (from perceptions of events to memories), and the Causal (from cause to effect).
Gist of Idea
There are Thermodynamic, Psychological and Causal arrows of time
Source
Robin Le Poidevin (Travels in Four Dimensions [2003], 12 'Three')
Book Reference
Le Poidevin,Robin: 'Travels in Four Dimensions' [OUP 2003], p.206
A Reaction
It would be nice if one of these explained the other two. Le Poidevin rejects the Psychological arrow, and seems to favour the Causal. Since I favour taking time as a primitive, I'm inclined to think that the arrow is included in the deal.