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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 April 2024" is ten days after "15 April 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.
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.
Midnight is the transition time from one day to the next – the moment when the date changes, on the local official clock time for any particular jurisdiction. By clock time, midnight is the opposite of noon, differing from it by 12 hours.
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.
A year zero does not exist in the Anno Domini (AD) calendar year system commonly used to number years in the Gregorian calendar ; in this system, the year 1 BC is followed directly by year AD 1. However, there is a year zero in both the astronomical year numbering system, and the ISO 8601:2004 system, the interchange standard for all calendar numbering systems. There is also a year zero in most Buddhist and Hindu calendars.
Different conventions exist around the world for date and time representation, both written and spoken.
The ISO week date system is effectively a leap week calendar system that is part of the ISO 8601 date and time standard issued by the International Organization for Standardization (ISO) since 1988 and, before that, it was defined in ISO (R) 2015 since 1971. It is used (mainly) in government and business for fiscal years, as well as in timekeeping. This was previously known as "Industrial date coding". The system specifies a week year atop the Gregorian calendar by defining a notation for ordinal weeks of the year.
ISO 2014 is an international standard that was issued in April 1976, and superseded by ISO 8601 in June 1988. ISO 2014 was the standard that originally introduced the all-numeric date notation [YYYY]-[MM]-[DD] with the digits in order starting with the most significant digit first. It was technically identical to ISO Recommendation R 2014 from 1971.
Date and time notation around the world varies.
Date and time notation in Canada combines conventions from the United Kingdom, conventions from the United States, and conventions from France, often creating confusion. The Government of Canada specifies the ISO 8601 format for all-numeric dates. It recommends writing the time using the 24-hour clock (22:51) for maximum clarity in both Canadian English and Canadian French, but also allows the 12-hour clock (10:51 p.m.) in English.
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.
In Poland, the official system for representing dates and times follows the international ISO 8601 standard. However, in less official use, other conventions prevail, such as the day-month-year order and several Polish language abbreviations.
Date and time notation in Sweden mostly follows the ISO 8601 standard: dates are generally written in the form YYYY-MM-DD. Although this format may be abbreviated in a number of ways, almost all Swedish date notations state the month between the year and the day. Months are not capitalised when written. The week number may also be used in writing and in speech. Times are generally written using 24-hour clock notation, with full stops as separators, although 12-hour clock notation is more frequently used in speech.
Date and time notation in the United Kingdom records the date using the day–month–year format. The ISO 8601 format (1999-12-31) is increasingly used for all-numeric dates. The time can be written using either the 24-hour clock (23:59) or the 12-hour clock (11:59 p.m.).
The European Committee for Standardization (CEN) and (CENELEC) adopted ISO 8601 with EN 28601, now EN ISO 8601. As a European Norm, CEN and CENELEC member states are obligated to adopt the standard as national standard without alterations as well.
ISO 8601 has been adopted as BIS IS 7900:2001.
The most formal manner of expressing the full date and/or time in South Korea is to suffix each of the year, month, day, ante/post-meridiem indicator, hour, minute and second with the corresponding unit and separating each with a space:
The date and time in Australia are most commonly recorded using the day–month–year format and the 12-hour clock, although 24-hour time is used in some cases. For example, some public transport operators such as V/Line and Transport NSW use 24-hour time, although others use 12-hour time instead.
Date and time notation in Pakistan is based on the Gregorian and Islamic calendars. Pakistan has not officially adopted any time and date representation standard based on the ISO 8601.
References
- ↑ "SANS 8601:2009 (Ed. 2.00)". SABS Webstore. Archived from the original on 24 November 2021. Retrieved 22 August 2023.
- ↑ "First Day of the Week in Different Countries".
- ↑ "Current Week in South Africa - Savvy Time".
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