Time

My youngest daughter asked  me what the time was, so I told her it was the way we humans divide up the day into equal parts. This, she said, was not very helpful. It made me wonder too. I mean, what is time?  The way we measure time is so arbitrary. For instance, the year we are in, 2012, what does that actually mean? 2012 years since someone was born, or from when he died (only apparently he didn't die, so how would you start the calendar?). Well, no it isn't, the calendar has been changed a few times since then. And the best guess is that it is between at least 4 and 40 years out. For any system of measurement, it's that's not very accurate. The Roman calendar was even weirder, never did get my head around that one. In Saudia, it's 1433. Which probably accounts for a lot of things. Ok, so where would we count from? And does it matter? Well, as far as it goes, I suppose so long as we all agree on the start date, no worries, 2012 it is then.
As for time in the sense of seconds/minutes/hours, they are still arbitrary, but again we have 'agreed' on their duration, and use them to define other things. Even distances can be measured by time; In China I believe it is/was, distances were measured by time, this made it possible for the distance between two places be different, depending if you were travelling up hill or down. Which actually makes sense if you are travelling on foot.

See also: http://en.wikipedia.org/wiki/Time