Книга: Time Measurement Systems: Iso 8601, Metric Time, Unix Time, 12-Hour Clock, 24-Hour Clock, Decimal Time, Thai Six-Hour Clock

Purchase includes free access to book updates online and a free trial membership in the publisher's book club where you can select from more than a million books without charge. Chapters: Iso 8601, Metric Time, Unix Time, 12-Hour Clock, 24-Hour Clock, Decimal Time, Thai Six-Hour Clock, Swatch Internet Time, Watch System, Ship's Bell, New Earth Time, Hexadecimal Time, Ke. Excerpt: clock system The 12-hour clock is a time conversion convention in which the 24 hours of the day are divided into two periods called ante meridiem ( a.m. , Latin : 'before mid day' English : 'before noon') and post meridiem ( p.m. , Latin: 'after mid day' English: 'after noon'). Each period consists of 12 hours numbered: 12 (acting as zero), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 . The 12-hour clock was developed over time from the mid-second millennium BC to the 16th century AD and was once popular throughout Northern Europe , but is now used as the dominant system in many former British colonies , including the United States and Canada (the English-speaking part) and the Philippines as ex-colony of the USA. It is also used informally in most of the world. History and use Exeter Cathedral clock, showing the Double-XII numbering scheme. The 12-hour clock can be traced back as far as Mesopotamia and Ancient Egypt : Both an Egyptian sundial for daytime use and an Egyptian water clock for nighttime use were found in the tomb of Pharaoh Amenhotep I . Dating to c. 1500 BC, these clocks divided their respective times of use into 12 hours each. The Romans also used a 12-hour clock: daylight was divided into 12 equal hours (of, thus, varying length throughout the year) and the night was divided into four watches. The Romans numbered the morning hours originally in reverse. For example, '3 a.m.' or '3 hours ante meridiem ' meant 'three hours before noon', compared to the modern meaning of 'three hours after midnight'. The first mechanical clocks in the 14th century, if they had dials at all, showe...