An exploration of the history and science of timekeeping, from the earliest sundials to the latest atomic clocks. The book describes various methods and devices used to measure time, including mechanical clocks, water clocks, and astronomical observations. The author also explains the principles behind modern time standards like Greenwich Mean Time (GMT). This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.