I have never figured out time. All of my estimates are terrible. On occasion, my estimates have been right, but I chalk that up randomness. I really have no idea how long things will take.

The closest I've come to good estimates is to compare task sizes: "this new task looks to be about as big as that thing I did a month ago; it took me 4 days then, it will take me 4 days now." The problem is I'm bad at comparing task sizes also.