The 24-hour clock is a convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today. The 12-hour clock is, however, still dominant in a handful of countries, particularly in Australia, Canada (except Quebec), India, the Philippines and the United States. In many countries both time systems are used, although, 12 hour time is mostly used in vocal speech for ease of use, and 24 hour time is preferred in writing. 24-hour notation is also popularly referred to as military time or astronomical time in the United States and Canada, and in
... see moreThe 24-hour clock is a convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today. The 12-hour clock is, however, still dominant in a handful of countries, particularly in Australia, Canada (except Quebec), India, the Philippines and the United States. In many countries both time systems are used, although, 12 hour time is mostly used in vocal speech for ease of use, and 24 hour time is preferred in writing. 24-hour notation is also popularly referred to as military time or astronomical time in the United States and Canada, and in Australia (though rarely). In some parts of the world, it is called railway time or continental time . It is also the international standard notation of time (ISO 8601). In the practice of medicine, the 24-hour clock is generally used in documentation of care as it precludes any ambiguity as to what time events occurred in the patient's medical history.
Description
A time of day is written in the 24-hour notation in the form hh:mm (for example 01:23) or hh:mm:ss (for example, 01:23:45), where hh (00 to 23) is the number of full hours that have passed since midnight, mm (00 to 59) is the number of full minutes that have passed since the last full hour, and ss (00 to 59) is the number of seconds since the last full minute. In the case of a leap second, the value of ss may extend to 60. A leading zero is added for numbers under 10. This zero is optional for the hours, but very commonly used in computer applications, where many specifications require it (for example, ISO 8601). Where subsecond resolution is required, the seconds can be a decimal fraction, that is, the fractional part follows a decimal dot or comma, as in 01:23:45.678. The most commonly used separator symbol between hours, minutes and seconds is the colon, which is also the symbol used in ISO 8601. In the past, some European countries used the dot on the line as a separator, but most national standards on time notation have since then been changed to the international standard colon. In some contexts (e.g., U.S. military, some computer protocols), no separator is used (e.g., 2359) and in some jurisdictions (France and Quebec) the letter h (for "heure") is used when indicating hours and minutes only (18h45).
Midnight 00:00 and 24:00
In the 24-hour time notation, the day begins at midnight, 00:00, and the last minute of the day begins at 23:59. Where convenient, the notation 24:00 may also be used to refer to midnight at the end of a given date—that is, 24:00 of some day is the same time as 00:00 of the following day.
The notation 24:00 mainly serves ...
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