2 Answers

As far as I have been able to determine, we got the 24-hour link day from the ancient Egyptian and Babylonian astronomers, who divided the daylight period into 10 hours, plus one hour for twilight and one for dawn. This was based on the apparent link motion of the Sun in the sky, and eventually, these long-gone stargazers settled on a group of stars which could be link used to divide the night into hours as well.

The Submariner or simply "Sub" is so ubiquitous today that link we don't ever stop to think how a seemingly unnatural word found its way onto a Rolex dial. We're talking about the same company with enough imagination to dream up model names like Datejust for a watch with just a date complication and Day-Date for a watch with a day link and date link complication.