Quote Originally Posted by Duck on Wheels View Post
Uhmmmm, lessee if I remember from my Geography major 35 years ago. Time zones are a compromise between two kinds of precision, social and natural. Do we all want to agree on what time it is? Or do we want time to make sense in terms of the height of the sun, rotation of the planet etc. To agree on what time it is over decent chunks of geographical space, we've made these more or less arbitrary divisions into "hours". Why hours? Why 24? Why not 20? Or 50? or 11? Historians have discussed how this happened, but basically it was an arbitrary decision that worked well enough given the ways clocks had developed up to then and the speeds and distances folks travelled back when the decisions were made.

Back then there was political rivalry over where to start counting. Paris? London? Again, historians can tell you how it wound up being Greenwich, but whatever the specifics the decision was political, and in that sense arbitrary.

Why do the zone lines make zigs and zags? Why have some places added or subtracted half an hour? That has to do with local adjustments so that time in some politically important place or across some functional social area is uniform and matches reasonably well with the height of the sun. After all, dividing the circumfrence of the earth into 24 exactly equal and straight-edged sections starting at Greenwich would make for some strange situations, like an hour's difference between one side of a street and another, or even one side of the bed and another. So local adjustments have been made.

Does that make sense now? If so, then I'm probably remembering it correctly. If not, I'll have to go back and look it up.

Thanks Duck, that makes sense. I looked at a map of the world timezones and noticed that you are right, there are a few areas that are a half an hour off from everywhere else. It's also interesting that the ENTIRE Indian Subcontinent is in the same time zone and not divided up.