Well, it's complicated in the sense that you couldn't work out the conversion without a computer, but on the other hand it's simple in the sense that the only p

Well, it's complicated in the sense that you couldn't work out the conversion without a computer, but on the other hand it's simple in the sense that the only parameters would be position on the Earth's surface and date/time. Also, I've read that counting 12 hours from sunrise to sunset was in fact how several ancient peoples did it. They didn't even necessarily count hours at night, only watches.