Recently I was listening to a discussion where someone was trying to explain her synesthesia about time to a bunch of people who didn't experience that. I found it really hard to wrap my head around, but there is a picture in this article of how one person visualizes time over the course of a year. The idea is just so far from what I think of as normal that it is difficult to really grasp.
"I thought everyone thought like I did, says Holly Branigan, also a scientist at Edinburgh University, and someone with time-space synaesthesia.
"I found out when I attended a talk in the department that Julia was giving. She said that some synaesthetes can see time. And I thought, 'Oh my god, that means I've got synaesthesia'." http://news.bbc.co.uk/2/hi/8248589.stm