Unix time

Unix time, or POSIX time, is a system for describing points in time. It is widely used not only on Unix-like operating systems but in many other computing systems, including the Java programming language. It is an encoding of UTC, and is sufficiently similar to a linear representation of the passage of time that it is frequently mistaken for one. The main complication is the leap seconds of UTC time. Unix time - Definition. There are two layers of encoding that make up Unix time, and they can be usef ...

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• Unix time - Definition
• Unix time - Encoding time as a number
• Unix time - Representing the number
• Unix time - UTC basis
• Unix time - History
• Unix time - 32-bit overflow
• Unix time - time_t parties

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There are two layers of encoding that make up Unix time, and they can be usefully separated. The first layer encodes a point in time as a scalar real number, and the second encodes that number as a sequence of bits or in some other manner. Unix time - Encoding time as a number. Modern Unix time is based strictly on UTC. UTC counts time using SI seconds, and breaks up the span of time into days. UTC days are mostly 86400 s long, but are occasionally 86401 s and could be 86399 s long (though the la ...

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Unix time, Unix time - Definition, Unix time - Encoding time as a number, Unix time - Representing the number, Unix time - UTC basis, Unix time - History, Unix time - 32-bit overflow, Unix time - time_t parties

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In computing, the year 2038 problem may cause some computer software to fail in or about the year 2038. The problem affects programs that use the POSIX time representation, which represents time as the number of seconds (ignoring leap seconds) since January 1, 1970. This representation is standard in Unix-like operating systems and also affects software written for most other operating systems because of the broad deployment of C. On most 32-bit systems, the time_t data type used to store this second count is a signed 32-bit ...

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Decimal time - Egypt. Decimal time was said to have been introduced in Ancient Egypt by Thoth. The day was divided into 10 parts, each part into 100 subdivisions, each further divided by 100, making 100,000 divisions in a day. Additionally, each Egyptian month was divided into three periods of 10 days called decans, and each of the 36 decans of the year was represented by a different constellation.

Decimal time, Decimal time - History, Decimal time - Egypt, Decimal time - China, Decimal time - France, Decimal time - Conversions, Decimal time - Fractional days, Decimal time - Swatch Internet Time, Decimal time - Other decimal times

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2009 (MMIX) is a common year starting on Thursday of the Gregorian calendar. It corresponds to 5769 and 5770 in the Hebrew Calendar and 1430-1431 in the Islamic Calendar. It is the Bicentennial of the births of Louis Braille, Charles Darwin, Edward Fitzgerald, William Gladstone, Maxim Gorki, Oliver Wendell Holmes, Sr., Abraham Lincoln, Felix Mendelssohn, Edgar Allan Poe, and Alfred, Lord Tennyson. Template:2009 by topic 2009 - Events. 2009 - January-April. ...

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There are exactly 86400 standard seconds (see SI for the current definition of the standard second) in a standard day, but in the French decimal time system there are 100,000 decimal seconds in the day, so the decimal second is shorter than its counterpart. One decimal second is 86400/100000 = 0.864 standard seconds. One decimal minute is 1440/1000 = 1.44 standard minutes, i.e. 1 minute 26.4 seconds. One decimal hour is 24/10 = 2.4 standard hours. The average adult human heart rate is close to 1 beat per decimal second, or 100 beats per decimal minute. One hundredth of a day is 14 minu ...

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Decimal time, Decimal time - History, Decimal time - Egypt, Decimal time - China, Decimal time - France, Decimal time - Conversions, Decimal time - Fractional days, Decimal time - Swatch Internet Time, Decimal time - Other decimal times

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The most common use of decimal time of day is as fractional days used by scientists and computer programmers. Standard 24-hour time is converted into a fractional day simply by dividing the number of hours elapsed since midnight by 24 to make a decimal fraction. Thus, midnight is 0.0 day, noon is 0.5 d, etc., which can be added to any type of date, including: Gregorian dates: 2000 January 1.5 ordinal dates: 00001.5 Julian dates: 24515 ...

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Decimal time, Decimal time - History, Decimal time - Egypt, Decimal time - China, Decimal time - France, Decimal time - Conversions, Decimal time - Fractional days, Decimal time - Swatch Internet Time, Decimal time - Other decimal times

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Numerous individuals have proposed variations of decimal time, dividing the day into different numbers of units and subunits with different names. Most are based upon fractional days, so that one decimal time format may be easily converted into another, such that all the following are equivalent: 0.500 fractional day 5:00 French decimal time @500 Swatch Internet Time ...

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Decimal time, Decimal time - History, Decimal time - Egypt, Decimal time - China, Decimal time - France, Decimal time - Conversions, Decimal time - Fractional days, Decimal time - Swatch Internet Time, Decimal time - Other decimal times

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11th millennium and beyond - Eras. 428,899: The last year of the Kali Yuga, the current and last of four Hindu Yugas (eras). 11th millennium and beyond - Technology. December 4, 292,277,026,596: 64-bit Unix time resets to zero. 11th millennium and beyond - Astronomical events. This section will list several rare astronomical events happening after the year 10000. All dates are in a uniform time scale like Terr ...

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• 11th millennium and beyond - Coincidences of nodes of planets
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• 11th millennium and beyond - Occultations of bright stars by planets

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Each calendar era starts from an arbitrary epoch, which is often chosen to commemorate an important historical or mythological event. For example, the epoch of the current civil calendar is the traditionally-reckoned year of the birth of Jesus, defined as year number 1. Thus, the first instant of January 1, 2006 CE should be exactly 2005 years since the epoch, but quirks in the development of the modern Gregorian calendar make this technically incorrect. The traditional Chinese calendar uses 2637 BCE, a date in the life of the legendary Yellow Emperor, as its epoch. Several other calendars are also curre ...

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Epoch reference date, Epoch reference date - Calendars, Epoch reference date - Astronomy, Epoch reference date - Computing, Epoch reference date - Trivia

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Leap seconds are necessary because time is measured utilizing stable atomic clocks (TAI or International Atomic Time), whereas the rotation of the Earth has been slowing down. Traditionally, the second has been defined as 1/86400 of a mean solar day (see solar time). This is determined by the rotation of the Earth around its axis and its orbit around the Sun; time was measured by astronomical observations. However, the solar day has gradually become 1.7 ms longer every ...

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Leap second, Leap second - Reason for leap seconds, Leap second - Announcement of leap seconds, Leap second - Proposal to redefine UTC and abolish leap seconds

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2009 - January-April. January 1 - Bulgaria and Slovakia are set to adopt the Euro January 1 - Deadline by which goods in all member states of the European Union must be sold in metric units (this has already been completed everywhere, except in the UK). Road signs in the UK are unaffected (road signs in all other member states will already be in metric units). January 20 - The next President of the United States (elected November 4, 2008) will be inaugurated. January 26 Annular so ...

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2009, 2009 - Events, 2009 - January-April, 2009 - May-December, 2009 - Unknown dates, 2009 - 2009 in Fiction

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The announcement to insert a leap second is usually issued whenever the difference between UTC and UT1 approaches 0.7s, to keep the difference between UTC and UT1 from exceeding ±0.9 s. After UTC 23:59:59, a positive leap second at 23:59:60 would be counted, before the clock indicates 00:00:00 of the next day. Negative leap seconds are also possible should the Earth's rotation become slightly f ...

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Leap second, Leap second - Reason for leap seconds, Leap second - Announcement of leap seconds, Leap second - Proposal to redefine UTC and abolish leap seconds

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On July 5, 2005, the Head of the Earth Orientation Center of the IERS sent a notice to IERS Bulletins C and D subscribers, soliciting comments on a proposal before the ITU-R Study Group 7's WP7-A to eliminate leap seconds from the UTC broadcast standard before 2008. (The ITU-R is responsible for the definition of UTC). The Wall Street Journal noted that the proposal was considered by a US official to be a private matter internal to the ITU as of July, 2005. It was expected to be considered in November, 2005, but the discussion has sin ...

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Leap second, Leap second - Reason for leap seconds, Leap second - Announcement of leap seconds, Leap second - Proposal to redefine UTC and abolish leap seconds

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Unix enthusiasts have a history of holding time_t parties to celebrate significant values of the Unix time number. These are directly analogous to the new year celebrations that occur at the change of year in many calendars. As the use of Unix time has spread, so has the practice of celebrating its milestones. Usually it is time values that are round numbers in decimal that are celebrated, following the Unix convention of viewing time_t values in decimal. Among some groups round binary numbers are also celebrated, such as +230 which ...

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Unix time, Unix time - Definition, Unix time - Encoding time as a number, Unix time - Representing the number, Unix time - UTC basis, Unix time - History, Unix time - 32-bit overflow, Unix time - time_t parties

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The earliest versions of Unix time had a 32-bit integer incrementing at a rate of 60 Hz, which was the rate of the system clock on the hardware of the early Unix systems. The value 60 Hz still appears in some software interfaces as a result. The epoch also differed from the current value. The first edition Unix Programmer's Manual dated November 3, 1971 defines the Unix time as "the time since 00:00:00, Jan. 1, 1971, measured in sixtieths of a second". It also comments that "the chronologically-minded user will note that 232See also:

Unix time, Unix time - Definition, Unix time - Encoding time as a number, Unix time - Representing the number, Unix time - UTC basis, Unix time - History, Unix time - 32-bit overflow, Unix time - time_t parties

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At 03:14:08 UTC on January 19, 2038 (+231), a 32-bit signed integer representation of Unix time will overflow. Systems using a 32-bit signed integer Unix time_t will therefore be unable to represent that time, or any later, and will likely wrap around to 20:45:52 UTC on December 13, 1901, with integer value -231. This is known as the year 2038 problem. Programs which must handle times beyond the overflow date will need to be changed to use a 64-bit time_t, a bignum representation of Unix time, or so ...

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Unix time, Unix time - Definition, Unix time - Encoding time as a number, Unix time - Representing the number, Unix time - UTC basis, Unix time - History, Unix time - 32-bit overflow, Unix time - time_t parties

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