87-706: Travel time ( h : mm ) The Friendship Express ( Turkish : Dostluk Ekspresi , Greek : Εξπρές Φιλίας , Exprés Filías ), was an international InterCity train jointly operated by the Turkish State Railways (TCDD) and TrainOSE from July 2005 to February 2011, linking Istanbul 's Sirkeci Terminal , Turkey and Thessaloniki , Greece. Eastbound trains (service 444/81021) departed daily at 19:48 from Thessaloniki arriving to Istanbul at 08:07. Westbound trains (service 81022/445) departed at 20:30 from Istanbul, arriving to Thessaloniki at 09:33. There were two trains on this service, one provided by TrainOSE and
174-566: A vigil was kept. The word "Vigils", at first applied to the Night Office, comes from a Latin source, namely the Vigiliae or nocturnal watches or guards of the soldiers. The night from six o'clock in the evening to six o'clock in the morning was divided into four watches or vigils of three hours each, the first, the second, the third, and the fourth vigil. The Horae were originally personifications of seasonal aspects of nature, not of
261-498: A fifth of the time from sunset to sunrise . Imperial China continued to use ke and geng but also began to divide the day into 12 "double hours" ( t 時 , s 时 , oc * də , p shí , lit. "time[s]") named after the earthly branches and sometimes also known by the name of the corresponding animal of the Chinese zodiac . The first shi originally ran from 11 pm to 1 am but
348-449: A fixed frame of reference (such as the fixed stars, Latin sidera , singular sidus ). Its average duration is 365.256 363 004 days (365 d 6 h 9 min 9.76 s) (at the epoch J2000.0 = January 1, 2000, 12:00:00 TT ). Today the mean tropical year is defined as the period of time for the mean ecliptic longitude of the Sun to increase by 360 degrees. Since the Sun's ecliptic longitude
435-626: A leap year there are 366 days. A leap year occurs every fourth year during which a leap day is intercalated into the month of February. The name "Leap Day" is applied to the added day. In astronomy, the Julian year is a unit of time defined as 365.25 days, each of exactly 86,400 seconds ( SI base unit ), totaling exactly 31,557,600 seconds in the Julian astronomical year. The Revised Julian calendar , proposed in 1923 and used in some Eastern Orthodox Churches , has 218 leap years every 900 years, for
522-435: A person carrying a bundle of wheat denoting "harvest". Slavic besides godŭ "time period; year" uses lěto "summer; year". Astronomical years do not have an integer number of days or lunar months. Any calendar that follows an astronomical year must have a system of intercalation such as leap years. In the Julian calendar , the average (mean) length of a year is 365.25 days. In a non-leap year, there are 365 days, in
609-710: A reference event in the past (called the epoch ) as the beginning of the era. The Gregorian calendar era is the world's most widely used civil calendar . Its epoch is a 6th century estimate of the date of birth of Jesus of Nazareth . Two notations are used to indicate year numbering in the Gregorian calendar: the Christian " Anno Domini " (meaning "in the year of the Lord"), abbreviated AD; and " Common Era ", abbreviated CE, preferred by many of other faiths and none. Year numbers are based on inclusive counting , so that there
696-416: A secondary unit computed as precisely 3,600 seconds. However, an hour of Coordinated Universal Time (UTC), used as the basis of most civil time, has lasted 3,601 seconds 27 times since 1972 in order to keep it within 0.9 seconds of universal time , which is based on measurements of the mean solar day at 0° longitude . The addition of these seconds accommodates the very gradual slowing of the rotation of
783-565: A time interval in Julian years is a way to precisely specify an amount of time (not how many "real" years), for long time intervals where stating the number of ephemeris days would be unwieldy and unintuitive. By convention, the Julian year is used in the computation of the distance covered by a light-year . In the Unified Code for Units of Measure (but not according to the International Union of Pure and Applied Physics or
870-509: A year on Earth is the time taken for Earth to revolve around the Sun . Generally, a year is taken to mean a calendar year , but the word is also used for periods loosely associated with the calendar or astronomical year, such as the seasonal year , the fiscal year , the academic year , etc. The term can also be used in reference to any long period or cycle, such as the Great Year . Due to
957-631: Is "certain" this duodecimal division of the night followed the adoption of the Egyptian civil calendar , usually placed c. 2800 BC on the basis of analyses of the Sothic cycle , but a lunar calendar presumably long predated this and also would have had 12 months in each of its years. The coffin diagrams show that the Egyptians took note of the heliacal risings of 36 stars or constellations (now known as " decans "), one for each of
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#17327724992921044-765: Is a 12-month period used for calculating annual financial statements in businesses and other organizations. In many jurisdictions, regulations regarding accounting require such reports once per twelve months, but do not require that the twelve months constitute a calendar year. For example, in Canada and India the fiscal year runs from April 1; in the United Kingdom it runs from April 1 for purposes of corporation tax and government financial statements, but from April 6 for purposes of personal taxation and payment of state benefits; in Australia it runs from July 1; while in
1131-494: Is about 20 minutes shorter than the sidereal year. The mean tropical year is approximately 365 days, 5 hours, 48 minutes, 45 seconds, using the modern definition ( = 365.24219 d × 86 400 s). The length of the tropical year varies a bit over thousands of years because the rate of axial precession is not constant. The anomalistic year is the time taken for the Earth to complete one revolution with respect to its apsides . The orbit of
1218-534: Is an integral approximation to the year equaling 365 days, which wanders in relation to more exact years. Typically the vague year is divided into 12 schematic months of 30 days each plus 5 epagomenal days. The vague year was used in the calendars of Ethiopia , Ancient Egypt , Iran , Armenia and in Mesoamerica among the Aztecs and Maya . It is still used by many Zoroastrian communities. A heliacal year
1305-427: Is measured with respect to the equinox, the tropical year comprises a complete cycle of the seasons and is the basis of solar calendars such as the internationally used Gregorian calendar . The modern definition of mean tropical year differs from the actual time between passages of, e.g., the northward equinox, by a minute or two, for several reasons explained below. Because of the Earth's axial precession , this year
1392-637: Is named after the 19th-century German astronomer and mathematician Friedrich Bessel . The following equation can be used to compute the current Besselian epoch (in years): The TT subscript indicates that for this formula, the Julian date should use the Terrestrial Time scale, or its predecessor, ephemeris time . The exact length of an astronomical year changes over time. Numerical value of year variation Mean year lengths in this section are calculated for 2000, and differences in year lengths, compared to 2000, are given for past and future years. In
1479-471: Is no "year zero". Years before the epoch are abbreviated BC for Before Christ or BCE for Before the Common Era . In Astronomical year numbering , positive numbers indicate years AD/CE, the number 0 designates 1 BC/BCE, −1 designates 2 BC/BCE, and so on. Other eras include that of Ancient Rome , Ab Urbe Condita ("from the foundation of the city ), abbreviated AUC; Anno Mundi ("year of
1566-469: Is now used to count quarter-hours, rather than a separate unit. As with the Egyptian night and daytime hours, the division of the day into 12 shi has been credited to the example set by the rough number of lunar cycles in a solar year, although the 12-year Jovian orbital cycle was more important to traditional Chinese and Babylonian reckoning of the zodiac. In Thailand , Laos , and Cambodia ,
1653-815: Is the accusative singular ; annī is genitive singular and nominative plural; annō the dative and ablative singular) is from a PIE noun *h₂et-no- , which also yielded Gothic aþn "year" (only the dative plural aþnam is attested). Although most languages treat the word as thematic *yeh₁r-o- , there is evidence for an original derivation with an *-r/n suffix, *yeh₁-ro- . Both Indo-European words for year, *yeh₁-ro- and *h₂et-no- , would then be derived from verbal roots meaning "to go, move", *h₁ey- and *h₂et- , respectively (compare Vedic Sanskrit éti "goes", atasi "thou goest, wanderest"). A number of English words are derived from Latin annus , such as annual , annuity , anniversary , etc.; per annum means "each year", annō Dominī means "in
1740-413: Is the interval between the heliacal risings of a star. It differs from the sidereal year for stars away from the ecliptic due mainly to the precession of the equinoxes . The Sothic year is the heliacal year, the interval between heliacal risings, of the star Sirius . It is currently less than the sidereal year and its duration is very close to the Julian year of 365.25 days. The Gaussian year
1827-534: Is the sidereal year for a planet of negligible mass (relative to the Sun) and unperturbed by other planets that is governed by the Gaussian gravitational constant . Such a planet would be slightly closer to the Sun than Earth's mean distance. Its length is: The Besselian year is a tropical year that starts when the (fictitious) mean Sun reaches an ecliptic longitude of 280°. This is currently on or close to January 1. It
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#17327724992921914-539: Is the time taken for the Sun (as seen from the Earth) to complete one revolution with respect to the same lunar node (a point where the Moon's orbit intersects the ecliptic). The year is associated with eclipses : these occur only when both the Sun and the Moon are near these nodes; so eclipses occur within about a month of every half eclipse year. Hence there are two eclipse seasons every eclipse year. The average duration of
2001-527: The Didache recommends disciples to pray the Lord's Prayer three times a day; this practice found its way into the canonical hours as well. By the second and third centuries, such Church Fathers as Clement of Alexandria , Origen , and Tertullian wrote of the practice of Morning and Evening Prayer, and of the prayers at the third, sixth and ninth hours. In the early church, during the night before every feast,
2088-470: The Earth . In modern life, the ubiquity of clocks and other timekeeping devices means that segmentation of days according to their hours is commonplace. Most forms of employment , whether wage or salaried labour, involve compensation based upon measured or expected hours worked. The fight for an eight-hour day was a part of labour movements around the world. Informal rush hours and happy hours cover
2175-444: The International Union of Geological Sciences , see below), the symbol a (without subscript) always refers to the Julian year, a j , of exactly 31 557 600 seconds . The SI multiplier prefixes may be applied to it to form "ka", "Ma", etc. Each of these three years can be loosely called an astronomical year . The sidereal year is the time taken for the Earth to complete one revolution of its orbit , as measured against
2262-469: The Julian Date system, in which a new Julian Day begins at noon) is that the date doesn't change during a single night's observing. In the modern 12-hour clock , counting the hours starts at midnight and restarts at noon. Hours are numbered 12, 1, 2, ..., 11. Solar noon is always close to 12 noon (ignoring artificial adjustments due to time zones and daylight saving time ), differing according to
2349-472: The Proto-Indo-European noun *yeh₁r-om "year, season". Cognates also descended from the same Proto-Indo-European noun (with variation in suffix ablaut ) are Avestan yārǝ "year", Greek ὥρα ( hṓra ) "year, season, period of time" (whence " hour "), Old Church Slavonic jarŭ , and Latin hornus "of this year". Latin annus (a 2nd declension masculine noun; annum
2436-607: The United States the fiscal year of the federal government runs from October 1. An academic year is the annual period during which a student attends an educational institution . The academic year may be divided into academic terms , such as semesters or quarters. The school year in many countries starts in August or September and ends in May, June or July. In Israel the academic year begins around October or November, aligned with
2523-419: The ancient Near East as a variable measure of 1 ⁄ 12 of the night or daytime . Such seasonal hours , also known as temporal hours or unequal hours , varied by season and latitude . Equal hours or equinoctial hours were taken as 1 ⁄ 24 of the day as measured from noon to noon; the minor seasonal variations of this unit were eventually smoothed by making it 1 ⁄ 24 of
2610-534: The canonical hours of the Orthodox and Catholic Church . During daylight, these followed the pattern set by the three-hour bells of the Roman markets , which were succeeded by the bells of local churches. They rang prime at about 6 am, terce at about 9 am, sext at noon, nones at about 3 pm, and vespers at either 6 pm or sunset . Matins and lauds precede these irregularly in
2697-456: The determinative hieroglyph for "sun". Ancient China divided its day into 100 "marks" ( Chinese : 刻 , oc * kʰək , p kè ) running from midnight to midnight. The system is said to have been used since remote antiquity , credited to the legendary Yellow Emperor , but is first attested in Han -era water clocks and in the 2nd-century history of that dynasty . It
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2784-403: The equation of time by as much as fifteen minutes either way. At the equinoxes sunrise is around 6 a.m. ( Latin : ante meridiem , before noon), and sunset around 6 p.m. ( Latin : post meridiem , after noon). In the modern 24-hour clock , counting the hours starts at midnight, and hours are numbered from 0 to 23. Solar noon is always close to 12:00, again differing according to
2871-529: The mean solar day . Since this unit was not constant due to long term variations in the Earth's rotation, the hour was finally separated from the Earth's rotation and defined in terms of the atomic or physical second . In the modern metric system , hours are an accepted unit of time defined as 3,600 atomic seconds. However, on rare occasions an hour may incorporate a positive or negative leap second , effectively making it appear to last 3,599 or 3,601 seconds, in order to keep UTC within 0.9 seconds of UT1 ,
2958-409: The perigee of the Moon's orbit. This period is associated with the apparent size of the full moon , and also with the varying duration of the synodic month . The duration of one full moon cycle is: The lunar year comprises twelve full cycles of the phases of the Moon, as seen from Earth. It has a duration of approximately 354.37 days. Muslims use this for celebrating their Eids and for marking
3045-415: The seasonal tropics , the annual wet and dry seasons are recognized and tracked. A calendar year is an approximation of the number of days of the Earth's orbital period, as counted in a given calendar . The Gregorian calendar , or modern calendar, presents its calendar year to be either a common year of 365 days or a leap year of 366 days, as do the Julian calendars . For the Gregorian calendar,
3132-456: The 16th century. The Islamic day begins at sunset. The first prayer of the day ( maghrib ) is to be performed between just after sunset and the end of twilight. Until 1968 Saudi Arabia used the system of counting 24 equal hours with the first hour starting at sunset. For many centuries, up to 1925, astronomers counted the hours and days from noon, because it was the easiest solar event to measure accurately. An advantage of this method (used in
3219-424: The Earth is elliptical; the extreme points, called apsides, are the perihelion , where the Earth is closest to the Sun, and the aphelion , where the Earth is farthest from the Sun. The anomalistic year is usually defined as the time between perihelion passages. Its average duration is 365.259636 days (365 d 6 h 13 min 52.6 s) (at the epoch J2011.0). The draconic year, draconitic year, eclipse year, or ecliptic year
3306-441: The Earth's axial tilt , the course of a year sees the passing of the seasons , marked by changes in weather , the hours of daylight , and, consequently, vegetation and soil fertility . In temperate and subpolar regions around the planet, four seasons are generally recognized: spring , summer , autumn , and winter . In tropical and subtropical regions, several geographical sectors do not present defined seasons; but in
3393-401: The Egyptians divided the night into 12 equal intervals. These were seasonal hours , shorter in the summer than in the winter. Subsequently, the day was divided into intervals as well, which eventually became more important than the nightly intervals. These subdivisions of a day spread to Greece, and later to Rome. The ancient Greeks kept time differently than is done today. Instead of dividing
3480-725: The United Kingdom, and 200 for pupils in Australia. In India the academic year normally starts from June 1 and ends on May 31. Though schools start closing from mid-March, the actual academic closure is on May 31 and in Nepal it starts from July 15. Schools and universities in Australia typically have academic years that roughly align with the calendar year (i.e., starting in February or March and ending in October to December), as
3567-637: The United States, notably Boston Latin School , may divide the year into five or more marking periods. Some state in defense of this that there is perhaps a positive correlation between report frequency and academic achievement. There are typically 180 days of teaching each year in schools in the US, excluding weekends and breaks, while there are 190 days for pupils in state schools in Canada, New Zealand and
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3654-483: The appearance of the mechanical clock, which furthered the adoption of equal length hours. This is also the system used in Jewish law and frequently called " Talmudic hour " ( Sha'a Zemanit ) in a variety of texts. The Talmudic hour is one twelfth of time elapsed from sunrise to sunset, day hours therefore being longer than night hours in the summer; in winter they reverse. The Indic day began at sunrise. The term hora
3741-477: The average (mean) year length of 365.242 2222 days, close to the length of the mean tropical year, 365.242 19 days (relative error of 9·10). In the year 2800 CE, the Gregorian and Revised Julian calendars will begin to differ by one calendar day. The Gregorian calendar aims to ensure that the northward equinox falls on or shortly before March 21 and hence it follows the northward equinox year , or tropical year . Because 97 out of 400 years are leap years,
3828-595: The average length of the calendar year (the mean year) across the complete leap cycle of 400 years is 365.2425 days (97 out of 400 years are leap years). In English, the unit of time for year is commonly abbreviated as "y" or "yr". The symbol "a" (for Latin : annus , year) is sometimes used in scientific literature, though its exact duration may be inconsistent. English year (via West Saxon ġēar ( /jɛar/ ), Anglian ġēr ) continues Proto-Germanic *jǣran ( *j ē₁ ran ). Cognates are German Jahr , Old High German jār , Old Norse ár and Gothic jer , from
3915-556: The beginning of the first hour, the middle of the day was at the end of the sixth hour and sunset at the end of the twelfth hour. This meant that the duration of hours varied with the season. In the Northern hemisphere, particularly in the more northerly latitudes, summer daytime hours were longer than winter daytime hours, each being one twelfth of the time between sunrise and sunset. These variable-length hours were variously known as temporal, unequal, or seasonal hours and were in use until
4002-422: The clock . (10 am and 10 pm are both read as "ten o'clock".) Hours on a 24-hour clock ("military time") are expressed as "hundred" or "hundred hours". (1000 is read "ten hundred" or "ten hundred hours"; 10 pm would be "twenty-two hundred".) Fifteen and thirty minutes past the hour is expressed as "a quarter past" or "after" and "half past", respectively, from their fraction of the hour. Fifteen minutes before
4089-513: The division between night and day, and daily routines often began when light was sufficient. "Babylonian hours" divide the day and night into 24 equal hours, reckoned from the time of sunrise. They are so named from the false belief of ancient authors that the Babylonians divided the day into 24 parts, beginning at sunrise. In fact, they divided the day into 12 parts (called kaspu or "double hours") or into 60 equal parts. Sunrise marked
4176-407: The eclipse year is This term is sometimes erroneously used for the draconic or nodal period of lunar precession , that is the period of a complete revolution of the Moon's ascending node around the ecliptic: 18.612 815 932 Julian years ( 6 798 .331 019 days; at the epoch J2000.0). The full moon cycle is the time for the Sun (as seen from the Earth) to complete one revolution with respect to
4263-684: The effect of tidal deceleration of the Earth by the Moon , which gradually lengthens the Earth's days. During the French Revolution , a general decimalisation of measures was enacted, including decimal time between 1794 and 1800. Under its provisions, the French hour ( French : heure ) was 1 ⁄ 10 of the day and divided formally into 100 decimal minutes ( minute décimale ) and informally into 10 tenths ( décime ). Mandatory use for all public records began in 1794, but
4350-506: The end of the 24th hour. The clocks in church towers struck only from 1 to 12, thus only during night or early morning hours. This manner of counting hours had the advantage that everyone could easily know how much time they had to finish their day's work without artificial light . It was already widely used in Italy by the 14th century and lasted until the mid-18th century; it was officially abolished in 1755, or in some regions customary until
4437-530: The equation of time. At the equinoxes sunrise is around 06:00, and sunset around 18:00. The ancient Egyptians began dividing the night into wnwt at some time before the compilation of the Dynasty V Pyramid Texts in the 24th century BC. By 2150 BC ( Dynasty IX ), diagrams of stars inside Egyptian coffin lids—variously known as "diagonal calendars" or "star clocks"—attest that there were exactly 12 of these. Clagett writes that it
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#17327724992924524-560: The first hour started with the sunset Angelus bell (or at the end of dusk, i.e., half an hour after sunset, depending on local custom and geographical latitude). The hours were numbered from 1 to 24. For example, in Lugano, the sun rose in December during the 14th hour and noon was during the 19th hour; in June the sun rose during the 7th hour and noon was in the 15th hour. Sunset was always at
4611-428: The gates of each hour of the underworld, and Wadjet and the rearing cobra ( uraeus ) were also sometimes referenced as wnwt from their role protecting the dead through these gates. The Egyptian word for astronomer , used as a synonym for priest, was wnwty , "one of the wnwt ", as it were "one of the hours". The earliest forms of wnwt include one or three stars, with the later solar hours including
4698-540: The goal to create the Egnatia Railway As of late 2024, the Friendship Express was still not running. Hour An hour ( symbol : h ; also abbreviated hr ) is a unit of time historically reckoned as 1 ⁄ 24 of a day and defined contemporarily as exactly 3,600 seconds ( SI ). There are 60 minutes in an hour, and 24 hours in a day. The hour was initially established in
4785-491: The historical Jalali calendar , known as the Solar Hijri calendar (1925), is a purely solar calendar with an irregular pattern of leap days based on observation (or astronomical computation), aiming to place new year ( Nowruz ) on the day of vernal equinox (for the time zone of Tehran ), as opposed to using an algorithmic system of leap years. A calendar era assigns a cardinal number to each sequential year, using
4872-437: The hour divisions.) The original decans used by the Egyptians would have fallen noticeably out of their proper places over a span of several centuries. By the time of Amenhotep III ( c. 1350 BC), the priests at Karnak were using water clocks to determine the hours. These were filled to the brim at sunset and the hour determined by comparing the water level against one of its 12 gauges, one for each month of
4959-507: The hour may be expressed as "a quarter to", "of", "till", or "before" the hour. (9:45 may be read "nine forty-five" or "a quarter till ten".) In ancient Egypt the flooding of the Nile was, and still is, an important annual event, crucial for agriculture. It was accompanied by the rise of Sirius before the sunrise, and the appearance of 12 constellations across the night sky, to which the Egyptians assigned some significance. Influenced by this,
5046-554: The latter of which is based on measurements of the mean solar day . Hour is a development of the Anglo-Norman houre and Middle English ure , first attested in the 13th century. It displaced tide tīd , 'time' and stound stund , span of time . The Anglo-Norman term was a borrowing of Old French ure , a variant of ore , which derived from Latin hōra and Greek hṓrā ( ὥρα ). Like Old English tīd and stund , hṓrā
5133-554: The length of their pendula ). The use of 24 hours for the entire day meant hours varied much less and the clocks needed to be adjusted only a few times a month. The minor irregularities of the apparent solar day were smoothed by measuring time using the mean solar day , using the Sun's movement along the celestial equator rather than along the ecliptic . The irregularities of this time system were so minor that most clocks reckoning such hours did not need adjustment. However, scientific measurements eventually became precise enough to note
5220-543: The mean length of the Gregorian calendar year is 365.242 5 days; with a relative error below one ppm (8·10) relative to the current length of the mean tropical year ( 365.242 189 days) and even closer to the current March equinox year of 365.242 374 days that it aims to match. Historically, lunisolar calendars intercalated entire leap months on an observational basis. Lunisolar calendars have mostly fallen out of use except for liturgical reasons ( Hebrew calendar , various Hindu calendars ). A modern adaptation of
5307-745: The mid-19th century. The system of Italian hours can be seen on a number of clocks in Europe, where the dial is numbered from 1 to 24 in either Roman or Arabic numerals. The St Mark's Clock in Venice, and the Orloj in Prague are famous examples. It was also used in Poland , Silesia , and Bohemia until the 17th century. Its replacement by the more practical division into twice twelve ( equinoctial ) hours (also called small clock or civic hours) began as early as
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#17327724992925394-534: The morning hours; compline follows them irregularly before sleep; and the midnight office follows that. Vatican II ordered their reformation for the Catholic Church in 1963, though they continue to be observed in the Orthodox churches. When mechanical clocks began to be used to show hours of daylight or nighttime, their period needed to be changed every morning and evening (for example, by changing
5481-483: The other by TCDD. TrainOSE used OSE former SNCF type T2 sleeping cars while TCDD used TVS2000 type cars. The trains changed locomotives and crew at Pythio . This train service was terminated on 13 February 2011. This is due to cost cutting by Greek state-owned company TrainOSE . On 8 March 2016 Greece and Turkey signed an intergovernmental agreement for reconnecting the line Istanbul to Thessaloniki with an enhancement to Igoumenitsa (a town facing towards Italy) with
5568-618: The other countries of the Sinosphere . The 12 shi supposedly began to be divided into 24 hours under the Tang , although they are first attested in the Ming -era Book of Yuan . In that work, the hours were known by the same earthly branches as the shi , with the first half noted as its "starting" and the second as "completed" or "proper" shi . In modern China, these are instead simply numbered and described as "little shi ". The modern ke
5655-460: The practice of publicly announcing the daytime hours with a gong and the nighttime hours with a drum . It was abolished in Laos and Cambodia during their French occupation and is uncommon there now. The Thai system remains in informal use in the form codified in 1901 by King Chulalongkorn . The Vedas and Puranas employed units of time based on the sidereal day ( nakṣatra ahorātra ). This
5742-566: The priesthood of the gods and with their divine services. By the New Kingdom , each hour was conceived as a specific region of the sky or underworld through which Ra 's solar barge travelled. Protective deities were assigned to each and were used as the names of the hours. As the protectors and resurrectors of the sun, the goddesses of the night hours were considered to hold power over all lifespans and thus became part of Egyptian funerary rituals. Two fire-spitting cobras were said to guard
5829-605: The second month of the Hebrew calendar. Some schools in the UK, Canada and the United States divide the academic year into three roughly equal-length terms (called trimesters or quarters in the United States), roughly coinciding with autumn, winter, and spring. At some, a shortened summer session, sometimes considered part of the regular academic year, is attended by students on a voluntary or elective basis. Other schools break
5916-475: The southern hemisphere experiences summer from December to February. The Julian year, as used in astronomy and other sciences, is a time unit defined as exactly 365.25 days of 86,400 SI seconds each (" ephemeris days "). This is the normal meaning of the unit "year" used in various scientific contexts. The Julian century of 36 525 ephemeris days and the Julian millennium of 365 250 ephemeris days are used in astronomical calculations. Fundamentally, expressing
6003-512: The start of the fasting month of Ramadan . A Muslim calendar year is based on the lunar cycle. The Jewish calendar is also essentially lunar, except that an intercalary lunar month is added once every two or three years, in order to keep the calendar synchronized with the solar cycle as well. Thus, a lunar year on the Jewish (Hebrew) calendar consists of either twelve or thirteen lunar months. The vague year, from annus vagus or wandering year,
6090-437: The telegraph or similar means to transfer a time signal in a split-second), this issue is much less relevant. Astrolabes , sundials , and astronomical clocks sometimes show the hour length and count using some of these older definitions and counting methods. In ancient and medieval cultures, the counting of hours generally started with sunrise. Before the widespread use of artificial light, societies were more concerned with
6177-438: The ten-day "weeks" of their civil calendar. (12 sets of alternate "triangle decans" were used for the 5 epagomenal days between years.) Each night, the rising of eleven of these decans were noted, separating the night into 12 divisions whose middle terms would have lasted about 40 minutes each. (Another seven stars were noted by the Egyptians during the twilight and predawn periods, although they were not important for
6264-466: The time between one midnight and the next into 24 equal hours, they divided the time from sunrise to sunset into 12 "seasonal hours" (their actual duration depending on season), and the time from sunset to the next sunrise again in 12 "seasonal hours". Initially, only the day was divided into 12 seasonal hours and the night into three or four night watches. By the Hellenistic period the night
6351-522: The time of day. The list of 12 Horae representing the 12 hours of the day is recorded only in Late Antiquity , by Nonnus . The first and twelfth of the Horae were added to the original set of ten: Medieval astronomers such as al-Biruni and Sacrobosco , divided the hour into 60 minutes , each of 60 seconds ; this derives from Babylonian astronomy , where the corresponding terms denoted
6438-514: The time required for the Sun's apparent motion through the ecliptic to describe one minute or second of arc, respectively. In present terms, the Babylonian degree of time was thus four minutes long, the "minute" of time was thus four seconds long and the "second" 1/15 of a second. In medieval Europe, the Roman hours continued to be marked on sundials but the more important units of time were
6525-594: The times of day when commuting slows down due to congestion or alcoholic drinks being available at discounted prices. The hour record for the greatest distance travelled by a cyclist within the span of an hour is one of cycling 's greatest honours. Many different ways of counting the hours have been used. Because sunrise, sunset, and, to a lesser extent, noon, are the conspicuous points in the day, starting to count at these times was, for most people in most early societies, much easier than starting at midnight. However, with accurate clocks and modern astronomical equipment (and
6612-515: The traditional system of noting hours is the six-hour clock . This reckons each of a day's 24 hours apart from noon as part of a fourth of the day. The first hour of the first half of daytime was 7 am; 1 pm the first hour of the latter half of daytime; 7 pm the first hour of the first half of nighttime; and 1 am the first hour of the latter half of nighttime. This system existed in the Ayutthaya Kingdom , deriving its current phrasing from
6699-560: The world"), used for the Hebrew calendar and abbreviated AM; and the Japanese imperial eras . The Islamic Hijri year , (year of the Hijrah , Anno Hegirae abbreviated AH), is a lunar calendar of twelve lunar months and thus is shorter than a solar year. Financial and scientific calculations often use a 365-day calendar to simplify daily rates. A fiscal year or financial year
6786-454: The year into two main semesters, a first (typically August through December) and a second semester (January through May). Each of these main semesters may be split in half by mid-term exams, and each of the halves is referred to as a quarter (or term in some countries). There may also be a voluntary summer session or a short January session. Some other schools, including some in the United States, have four marking periods. Some schools in
6873-732: The year of the Lord". The Greek word for "year", ἔτος , is cognate with Latin vetus "old", from the PIE word *wetos- "year", also preserved in this meaning in Sanskrit vat-sa-ras "year" and vat-sa- "yearling (calf)", the latter also reflected in Latin vitulus "bull calf", English wether "ram" (Old English weðer , Gothic wiþrus "lamb"). In some languages, it is common to count years by referencing to one season, as in "summers", or "winters", or "harvests". Examples include Chinese 年 "year", originally 秂 , an ideographic compound of
6960-426: The year. During the New Kingdom , another system of decans was used, made up of 24 stars over the course of the year and 12 within any one night. The later division of the day into 12 hours was accomplished by sundials marked with ten equal divisions. The morning and evening periods when the sundials failed to note time were observed as the first and last hours. The Egyptian hours were closely connected both with
7047-647: Was also divided into 12 hours. The day-and-night ( νυχθήμερον ) was probably first divided into 24 hours by Hipparchus of Nicaea . The Greek astronomer Andronicus of Cyrrhus oversaw the construction of a horologion called the Tower of the Winds in Athens during the first century BCE. This structure tracked a 24-hour day using both sundials and mechanical hour indicators. The canonical hours were inherited into early Christianity from Second Temple Judaism . By AD 60,
7134-515: Was measured with sundials and water clocks . Into the Eastern Han , the Chinese measured their day schematically, adding the 20- ke difference between the solstices evenly throughout the year, one every nine days. During the night, time was more commonly reckoned during the night by the "watches" ( Chinese : 更 , oc * kæŋ , p gēng ) of the guard, which were reckoned as
7221-460: Was originally a vaguer word for any span of time, including seasons and years . Its Proto-Indo-European root has been reconstructed as *yeh₁- ("year, summer "), making hour distantly cognate with year . The time of day is typically expressed in English in terms of hours. Whole hours on a 12-hour clock are expressed using the contracted phrase o'clock , from the older of
7308-554: Was reckoned as starting at midnight by the time of the History of Song , compiled during the early Yuan . These apparently began to be used during the Eastern Han that preceded the Three Kingdoms era, but the sections that would have covered them are missing from their official histories; they first appear in official use in the Tang -era Book of Sui . Variations of all these units were subsequently adopted by Japan and
7395-461: Was suspended six months later by the same 1795 legislation that first established the metric system. In spite of this, a few localities continued to use decimal time for six years for civil status records, until 1800, after Napoleon's Coup of 18 Brumaire. The metric system bases its measurements of time upon the second , defined since 1952 in terms of the Earth's rotation in AD 1900. Its hours are
7482-475: Was used to indicate an hour. The time was measured based on the length of the shadow at day time. A hora translated to 2.5 pe . There are 60 pe per day, 60 minutes per pe and 60 kshana (snap of a finger or instant) per minute. Pe was measured with a bowl with a hole placed in still water. Time taken for this graduated bowl was one pe . Kings usually had an officer in charge of this clock. In so-called " Italian time", "Italian hours", or "old Czech time",
7569-443: Was variously divided into 30 muhūrta-s of 48 minutes each or 60 dandas or nadī-s of 24 minutes each. The solar day was later similarly divided into 60 ghaṭikás of about the same duration, each divided in turn into 60 vinadis . The Sinhalese followed a similar system but called their sixtieth of a day a peya . Year A year is the time taken for astronomical objects to complete one orbit . For example,
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