This kind of 12-hour clock can be found in countries where the 24-hour clock is preferred. This modification allows the clock to also be read in 24-hour notation. The number 12 is paired either with a 00 or a 24, while the numbers 1 through 11 are paired with the numbers 13 through 23, respectively. Some analog clock dials have an inner ring of numbers along with the standard 1-to-12 numbered ring. Most analog clocks and watches today use the 12-hour dial, on which the shorter hour hand rotates once every 12 hours and twice in one day. The 24-hour analog dial was reserved for more specialized applications, such as astronomical clocks and chronometers. The 12-hour clock was used throughout the British empire.ĭuring the 15th and 16th centuries, the 12-hour analog dial and time system gradually became established as standard throughout Northern Europe for general public use. This is known as the double-XII system and can be seen on many surviving clock faces, such as those at Wells and Exeter.Įlsewhere in Europe, numbering was more likely to be based on the 24-hour system (I to XXIV). In Northern Europe these dials generally used the 12-hour numbering scheme in Roman numerals but showed both a.m. The first mechanical clocks in the 14th century, if they had dials at all, showed all 24 hours using the 24-hour analog dial, influenced by astronomers' familiarity with the astrolabe and sundial and by their desire to model the Earth's apparent motion around the Sun. The Romans also used a 12-hour clock: daylight was divided into 12 equal hours (thus hours having varying length throughout the year) and the night was divided into four watches. 1500 BC, these clocks divided their respective times of use into 12 hours each. Both an Egyptian sundial for daytime use and an Egyptian water clock for night-time use were found in the tomb of Pharaoh Amenhotep I. The 12-hour clock can be traced back as far as Mesopotamia and ancient Egypt. Noon itself is rarely abbreviated today but if it is, it is denoted "m." This eventually evolved into the two 12-hour periods which are used today, one called "a.m." starting at midnight and another called "p.m." starting at noon. Originally there were two cycles: one cycle which could be tracked by the position of the Sun (day), followed by one cycle which could be tracked by the Moon and stars (night). The natural day-and-night division of a calendar day forms the fundamental basis as to why each day is split into two cycles. History and use Exeter Cathedral Astronomical Clock, showing the double-XII numbering scheme There is no widely accepted convention for how midday and midnight should be represented: in English-speaking countries, "12 p.m." indicates 12 o'clock noon, while "12 a.m." means 12 o'clock midnight. The 12-hour time convention is common in several English-speaking nations and former British colonies, as well as a few other countries. The 12-hour clock was developed from the second millennium BC and reached its modern form in the 16th century. (from Latin post meridiem, translating to "after midday"). (from Latin ante meridiem, translating to "before midday") and p.m. The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. For the meridian 180° both east and west of the prime meridian in a geographical coordinate system, see antimeridian. Or, ( 60 - 35 = 25 minutes) 25 minutes to 9."Ante meridiem" redirects here. In figure (iii) expresses 8 : 35 or 35 minutes past 8 The minute hand is 2 divisions after number 8. In figure (ii) hour hand is between 3 and 4. If minute hand indicates 3 divisions after number 7, then Multiplied by 5 and number of divisions after the number, express the The watch indicates that the time is 1 hour 19 minutes.Īt or after the number that the hour-hand indicates, the number expresses the hour.Īt or after the number that the minute-hand indicates, the number The minute hand indicates 4 divisions after the number 3, i.e., 3 x 5 + 4 = 19, or 19 divisions from 12. In figure (i) hour-hand is indicating number 1 or just after 1. Hour hand indicates hours and Minute-hand indicates minutes.
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