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A calendar date is a reference to a particular day represented within a calendar system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "25 June 2024" is ten days after "15 June 2024". The date of a particular event depends on the observed time zone. For example, the air attack on Pearl Harbor that began at 7:48 a.m. Hawaiian time on 7 December 1941 took place at 3:18 a.m. Japan Standard Time, 8 December in Japan.
ISO 8601 is an international standard covering the worldwide exchange and communication of date and time-related data. It is maintained by the International Organization for Standardization (ISO) and was first published in 1988, with updates in 1991, 2000, 2004, and 2019, and an amendment in 2022. The standard provides a well-defined, unambiguous method of representing calendar dates and times in worldwide communications, especially to avoid misinterpreting numeric dates and times when such data is transferred between countries with different conventions for writing numeric dates and times.
A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.
The modern 24-hour clock is the convention of timekeeping in which the day runs from midnight to midnight and is divided into 24 hours. This is indicated by the hours passed since midnight, from 00(:00) to 23(:59), with 24(:00) as an option to indicate the end of the day. This system, as opposed to the 12-hour clock, is the most commonly used time notation in the world today, and is used by the international standard ISO 8601.
The year 2038 problem and the year 2106 problem are time computing problems that leave some computer systems unable to represent times after 03:14:07 UTC on 19 January 2038 and 06:28:15 UTC on 7 February 2106 respectively.
Swatch Internet Time is a decimal time system introduced in 1998 by the Swatch corporation as part of their marketing campaign for their line of ".beat" watches. Those without a watch can use the Internet to view the current time on the watchmaker's website. The concept is similar to decimal minutes in French Revolutionary decimal time.
Computer-aided dispatch (CAD), also called computer-assisted dispatch, is a method of dispatching taxicabs, couriers, field service technicians, mass transit vehicles or emergency services assisted by computer. It can either be used to send messages to the dispatchee via a mobile data terminal (MDT) and/or used to store and retrieve data. A dispatcher may announce the call details to field units over a two-way radio. Some systems communicate using a two-way radio system's selective calling features. CAD systems may send text messages with call-for-service details to alphanumeric pagers or wireless telephony text services like SMS. The central idea is that persons in a dispatch center are able to easily view and understand the status of all units being dispatched. CAD provides displays and tools so that the dispatcher has an opportunity to handle calls-for-service as efficiently as possible.
A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolute notion of time, however. They can have any epoch, can be relative to any arbitrary time, such as the power-on time of a system, or to some arbitrary time in the past.
Unix time is a date and time representation widely used in computing. It measures time by the number of non-leap seconds that have elapsed since 00:00:00 UTC on 1 January 1970, the Unix epoch. In modern computing, values are sometimes stored with higher granularity, such as microseconds or nanoseconds.
NAVTEX, sometimes styled Navtex or NavTex, is an international automated medium frequency direct-printing service for delivery of navigational and meteorological warnings and forecasts, as well as urgent maritime safety information (MSI) to ships.
The airline teletype system uses teleprinters, which are electro-mechanical typewriters that can communicate typed messages from point to point through simple electric communications channels, often just pairs of wires. The most modern form of these devices are fully electronic and use a screen, instead of a printer.
A dimension is a structure that categorizes facts and measures in order to enable users to answer business questions. Commonly used dimensions are people, products, place and time.
The tz database is a collaborative compilation of information about the world's time zones and rules for observing daylight saving time, primarily intended for use with computer programs and operating systems. Paul Eggert has been its editor and maintainer since 2005, with the organizational backing of ICANN. The tz database is also known as tzdata, the zoneinfo database or the IANA time zone database, and occasionally as the Olson database, referring to the founding contributor, Arthur David Olson.
Date and time notation around the world varies.
In computer science, data type limitations and software bugs can cause errors in time and date calculation or display. These are most commonly manifestations of arithmetic overflow, but can also be the result of other issues. The most well-known consequence of this type is the Y2K problem, but many other milestone dates or times exist that have caused or will cause problems depending on various programming deficiencies.
The military time zones are a standardized, uniform set of time zones for expressing time across different regions of the world, named after the NATO phonetic alphabet. The Zulu time zone (Z) is equivalent to Coordinated Universal Time (UTC) and is often referred to as the military time zone. The military time zone system ensures clear communication in a concise manner, and avoids confusion when coordinating across time zones. As the ACP 121 standard, the military time zone system is used by the armed forces for Australia, Canada, New Zealand, the United Kingdom, the United States, and many nations in NATO.
In computing, an epoch is a fixed date and time used as a reference from which a computer measures system time. Most computer systems determine time as a number representing the seconds removed from a particular arbitrary date and time. For instance, Unix and POSIX measure time as the number of seconds that have passed since Thursday 1 January 1970 00:00:00 UT, a point in time known as the Unix epoch. Windows NT systems, up to and including Windows 11 and Windows Server 2022, measure time as the number of 100-nanosecond intervals that have passed since 1 January 1601 00:00:00 UTC, making that point in time the epoch for those systems. Computing epochs are almost always specified as midnight Universal Time on some particular date.
A call detail record (CDR) is a data record produced by a telephone exchange or other telecommunications equipment that documents the details of a telephone call or other telecommunications transactions that passes through that facility or device. The record contains various attributes of the call, such as time, duration, completion status, source number, and destination number. It is the automated equivalent of the paper toll tickets that were written and timed by operators for long-distance calls in a manual telephone exchange.
Date and time notation in the United States differs from that used in nearly all other countries. It is inherited from one historical branch of conventions from the United Kingdom. American styles of notation have also influenced customs of date notation in Canada, creating confusion in international commerce.
Date and time notation in New Zealand most commonly records the date using the day-month-year format, while the ISO 8601 format (2024-06-05) is increasingly used for all-numeric dates, such as date of birth. The time can be written using either the 12-hour clock or the 24-hour clock (06:35).
References
- TM 20-205, the Dictionary of United States Army Terms (1944)
- ACP 121(I) p 3–7
