An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy, a calendar era used for a given calendar, or the geological eras defined for the history of Earth.

Comparable terms are epoch, age, period, saeculum, aeon (Greek aion) and Sanskrit yuga.


The word has been in use in English since 1615, and is derived from Late Latin aera "an era or epoch from which time is reckoned," probably identical to Latin æra "counters used for calculation," plural of æs "brass, money".

The Latin word use in chronology seems to have begun in 5th century Visigothic Spain, where it appears in the History of Isidore of Seville, and in later texts. The Spanish era is calculated from 38 BC, perhaps because of a tax (cfr. indiction) levied in that year, or due to a miscalculation of the Battle of Actium, which occurred in 31 BC.

Like epoch, "era" in English originally meant "the starting point of an age"; the meaning "system of chronological notation" is c.1646; that of "historical period" is 1741.

Use in chronology

In chronology, an era is the highest level for the organization of the measurement of time. A calendar era indicates a span of many years which are numbered beginning at a specific reference date (epoch), which often marks the origin of a political state or cosmology, dynasty, ruler, the birth of a leader, or another significant historical or mythological event; it is generally called after its focus accordingly as in Victorian era.

Geological era

In large-scale natural science, there is need for another time perspective, independent from human activity, and indeed spanning a far longer period (mainly prehistoric), where geologic era refers to well-defined time spans. The next-larger division of geologic time is the eon. The Phanerozoic Eon is subdivided into eras.[1] There are currently three eras defined in the Phanerozoic; the following table lists them from youngest to oldest (BP is an abbreviation for "before present").

Era[2][3] Beginning (millions of years BP) End (millions of years BP)
Cenozoic 66.038 N/A
Mesozoic 252.17 66.038
Paleozoic 542 252.17

The older Proterozoic and Archean eons are also divided into eras.

Cosmological era

For periods in the history of the universe, the term "epoch" is typically preferred, but "era" is used e.g. of the "Stelliferous Era".

Calendar eras

Calendar eras count the years since a particular date (epoch), often one with religious significance. Anno mundi ("year of the world") refers to a group of calendar eras based on a calculation of the age of the world, assuming it was created as described in the Book of Genesis. In Jewish religious contexts one of the versions is still used, and many Eastern Orthodox religious calendars used another version until 1728. Hebrew year 5772 AM began at sunset on 28 September 2011 and ended on 16 September 2012. In the Western church Anno Domini (=AD = CE), counting the years since the birth of Jesus on traditional calculations, was always dominant.

The Islamic calendar, which also has variants, counts years from the Hijra or emigration of the Islamic prophet Muhammad from Mecca to Medina, which occurred in 622 CE. The Islamic year is some days shorter than 365; January 2012 fell in 1433 AH ("After Hijra").

For a time ranging from 1872 to the Second World War, the Japanese used the imperial year system (kōki), counting from the year when the legendary Emperor Jimmu founded Japan which occurred in 660 BC.

Many Buddhist calendars count from the death of the Buddha, which according to the most commonly used calculations was in 545-543 BCE or 483 BCE. Dates are given as "BE" for "Buddhist Era"; 2000 CE was 2543 BE in the Thai solar calendar.

Other calendar eras of the past counted from political events, such as the Seleucid era and the Ancient Roman ab urbe condita ("AUC"), counting from the foundation of the city.

Regnal eras

The word era also denotes the units used under a different, more arbitrary system where time is not represented as an endless continuum with a single reference year, but each unit starts counting from one again as if time starts again. The use of regnal years is a rather impractical system, and a challenge for historians if a single piece of the historical chronology is missing, and often reflects the preponderance in public life of an absolute ruler in many ancient cultures. Such traditions sometimes outlive the political power of the throne, and may even be based on mythological events or rulers who may not have existed (for example Rome numbering from the rule of Romulus and Remus). In a manner of speaking the use of the supposed date of the birth of Christ as a base year is a form of an era.

In East Asia, each emperor's reign may be subdivided into several reign periods, each being treated as a new era. The name of each was a motto or slogan chosen by the emperor. Different East Asian countries utilized slightly different systems, notably:

A similar practice survived in the United Kingdom until quite recently, but only for formal official writings: in daily life the ordinary year A.D. has been used for a long time, but Acts of Parliament were dated according to the years of the reign of the current Monarch, so that "61 & 62 Vict c. 37" refers to the Local Government (Ireland) Act 1898 passed in the session of Parliament in the 61st/62nd year of the reign of Queen Victoria.


"Era" can be used to refer to well-defined periods in historiography, such as the Roman era, Elizabethan era, Victorian era, etc. Use of the term for more recent periods or topical history might include Soviet era, and "musical eras" in the history of modern popular music, such as the "Big Band era", "Disco era", etc.

See also


  1. ^ Short, N.M. (2009). "Geologic Time" Archived 2005-04-18 at the Wayback Machine in Remote Sensing Tutorial Archived 2009-10-27 at the Wayback Machine. NASA.
  2. ^ Lide, D. R. (1990). Handbook of Chemistry and Physics. Boca Raton: CRC Press. pp. 14-16.
  3. ^ "International Stratigraphic Chart". International Commission on Stratigraphy. Archived from the original on 30 May 2014.
Anno Domini

The terms anno Domini (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendars. The term anno Domini is Medieval Latin and means "in the year of the Lord", but is often presented using "our Lord" instead of "the Lord", taken from the full original phrase "anno Domini nostri Jesu Christi", which translates to "in the year of our Lord Jesus Christ".

This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus of Nazareth, with AD counting years from the start of this epoch, and BC denoting years before the start of the era. There is no year zero in this scheme, so the year AD 1 immediately follows the year 1 BC. This dating system was devised in 525 by Dionysius Exiguus of Scythia Minor, but was not widely used until after 800.The Gregorian calendar is the most widely used calendar in the world today. For decades, it has been the unofficial global standard, adopted in the pragmatic interests of international communication, transportation, and commercial integration, and recognized by international institutions such as the United Nations.Traditionally, English followed Latin usage by placing the "AD" abbreviation before the year number. However, BC is placed after the year number (for example: AD 2019, but 68 BC), which also preserves syntactic order. The abbreviation is also widely used after the number of a century or millennium, as in "fourth century AD" or "second millennium AD" (although conservative usage formerly rejected such expressions). Because BC is the English abbreviation for Before Christ, it is sometimes incorrectly concluded that AD means After Death, i.e., after the death of Jesus. However, this would mean that the approximate 33 years commonly associated with the life of Jesus would neither be included in the BC nor the AD time scales.Terminology that is viewed by some as being more neutral and inclusive of non-Christian people is to call this the Current or Common Era (abbreviated as CE), with the preceding years referred to as Before the Common or Current Era (BCE). Astronomical year numbering and ISO 8601 avoid words or abbreviations related to Christianity, but use the same numbers for AD years.


Apartheid (South African English: ; Afrikaans: [aˈpartɦəit], segregation; lit. "separateness") was a system of institutionalised racial segregation that existed in South Africa from 1948 until the early 1990s. Apartheid was characterised by an authoritarian political culture based on baasskap (or white supremacy), which encouraged state repression of Black African, Coloured, and Asian South Africans for the benefit of the nation's minority white population. The economic legacy and social effects of apartheid continue to the present day.Broadly speaking, apartheid was delineated into petty apartheid, which entailed the segregation of public facilities and social events, and grand apartheid, which dictated housing and employment opportunities by race. Prior to the 1940s, some aspects of apartheid had already emerged in the form of minority rule by White South Africans and the socially enforced separation of Black South Africans from other races, which later extended to pass laws and land apportionment. Apartheid was adopted as a formal policy by the South African government after the election of the National Party (NP) at the 1948 general election.A codified system of racial stratification began to take form in South Africa under the Dutch Empire in the late-eighteenth century, although informal segregation was present much earlier due to social cleavages between Dutch colonists and a creolised, ethnically diverse slave population. With the rapid growth and industrialisation of the British Cape Colony in the nineteenth century, racial policies and laws became increasingly rigid. Cape legislation that discriminated specifically against Black South Africans began appearing shortly before 1900. The policies of the Boer republics were also racially exclusive; for instance, the Transvaal's constitution barred Black and Coloured participation in church and state.The first apartheid law was the Prohibition of Mixed Marriages Act, 1949, followed closely by the Immorality Amendment Act of 1950, which made it illegal for most South African citizens to marry or pursue sexual relationships across racial lines. The Population Registration Act, 1950 classified all South Africans into one of four racial groups based on appearance, known ancestry, socioeconomic status, and cultural lifestyle: "Black", "White", "Coloured", and "Indian", the last two of which included several sub-classifications. Places of residence were determined by racial classification. From 1960–1983, 3.5 million Non-White South Africans were removed from their homes and forced into segregated neighbourhoods, in one of the largest mass evictions in modern history. Most of these targeted removals were intended to restrict the Black population to ten designated "tribal homelands", also known as bantustans, four of which became nominally independent states. The government announced that relocated persons would lose their South African citizenship as they were absorbed into the bantustans.Apartheid sparked significant international and domestic opposition, resulting in some of the most influential global social movements of the twentieth century. It was the target of frequent condemnation in the United Nations and brought about an extensive arms and trade embargo on South Africa. During the 1970s and 1980s, internal resistance to apartheid became increasingly militant, prompting brutal crackdowns by the National Party government and protracted sectarian violence that left thousands dead or in detention. Some reforms of the apartheid system were undertaken, including allowing for Indian and Coloured political representation in parliament, but these measures failed to appease most activist groups.Between 1987–1993, the National Party entered into bilateral negotiations with the African National Congress, the leading anti-apartheid political movement, for ending segregation and introducing majority rule. In 1990, prominent ANC figures such as Nelson Mandela were released from prison. Apartheid legislation was repealed on 17 June 1991, pending fully democratic, multiracial elections set for April 1994.

Classical music

Classical music is art music produced or rooted in the traditions of Western culture, including both liturgical (religious) and secular music. While a more precise term is also used to refer to the period from 1750 to 1820 (the Classical period), this article is about the broad span of time from before the 6th century AD to the present day, which includes the Classical period and various other periods. The central norms of this tradition became codified between 1550 and 1900, which is known as the common-practice period. The major time divisions of Western art music are as follows:

the ancient music period, before 500 AD

the early music period, which includes

the Medieval (500–1400) including

the ars antiqua (1170–1310)

the ars nova (1310–1377)

the ars subtilior (1360–1420)

the Renaissance (1400–1600) eras.

Baroque (1600–1750)

the galant music period (1720s–1770s)

the common-practice period, which includes

Baroque (1600–1750)

the galant music period (1720s–1770s)

Classical (1750–1820)

Romantic eras (c.1780–1910)

the 20th and 21st centuries (1901–present) which includes:

the modern (1890–1930) that overlaps from the late-19th century,

impressionism (1875 or 1890–1925) that also overlaps from the late-19th century

neoclassicism (1920–1950), predominantly in the inter-war period

the high modern (1930–present)

the postmodern (1930–present) eras

the experimental (1950–present)

contemporary (1945 or 1975–present)European art music is largely distinguished from many other non-European classical and some popular musical forms by its system of staff notation, in use since about the 11th century. Catholic monks developed the first forms of modern European musical notation in order to standardize liturgy throughout the worldwide Church. Western staff notation is used by composers to indicate to the performer the pitches (which form the melodies, basslines and chords), tempo, metre and rhythms for a piece of music. This can leave less room for practices such as improvisation and ad libitum ornamentation, which are frequently heard in non-European art music and in popular-music styles such as jazz and blues. Another difference is that whereas most popular styles adopt the song (strophic) form or a derivation of this form, classical music has been noted for its development of highly sophisticated forms of instrumental music such as the symphony, concerto, fugue, sonata, and mixed vocal and instrumental styles such as opera, cantata, and mass.The term "classical music" did not appear until the early 19th century, in an attempt to distinctly canonize the period from Johann Sebastian Bach to Ludwig van Beethoven as a golden age. The earliest reference to "classical music" recorded by the Oxford English Dictionary is from about 1829.

Common Era

Common Era or Current Era (CE) is one of the notation systems for the world's most widely used calendar era. BCE (Before the Common Era or Before the Current Era) is the era before CE. BCE and CE are alternatives to the Dionysian AD and BC system. The Dionysian era distinguishes eras using AD (anno Domini, "[the] year of [the] Lord") and BC ("before Christ"). Since the two notation systems are numerically equivalent, "2019 CE" corresponds to "AD 2019" and "400 BCE" corresponds to "400 BC". Both notations refer to the Gregorian calendar (and its predecessor, the Julian calendar). The year-numbering system utilized by the Gregorian calendar is used throughout the world today, and is an international standard for civil calendars.The expression has been traced back to 1615, when it first appeared in a book by Johannes Kepler as the Latin usage annus aerae nostrae vulgaris, and to 1635 in English as "Vulgar Era". The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. In the later 20th century, the use of CE and BCE was popularized in academic and scientific publications, and more generally by authors and publishers wishing to emphasize sensitivity to non-Christians, by not explicitly referencing Jesus as "Christ" and Dominus ("Lord") through use of the abbreviation "AD".

Edo period

The Edo period (江戸時代, Edo jidai) or Tokugawa period (徳川時代) is the period between 1603 and 1868 in the history of Japan, when Japanese society was under the rule of the Tokugawa shogunate and the country's 300 regional daimyō. The period was characterized by economic growth, strict social order, isolationist foreign policies, a stable population, "no more wars", and popular enjoyment of arts and culture. The shogunate was officially established in Edo on March 24, 1603, by Tokugawa Ieyasu. The period came to an end with the Meiji Restoration on May 3, 1868, after the fall of Edo.

Elizabethan era

The Elizabethan era is the epoch in the Tudor period of the history of England during the reign of Queen Elizabeth I (1558–1603). Historians often depict it as the golden age in English history. The symbol of Britannia (a female personification of Great Britain) was first used in 1572, and often thereafter, to mark the Elizabethan age as a renaissance that inspired national pride through classical ideals, international expansion, and naval triumph over Spain. The historian John Guy (1988) argues that "England was economically healthier, more expansive, and more optimistic under the Tudors" than at any time in a thousand years.This "golden age" represented the apogee of the English Renaissance and saw the flowering of poetry, music and literature. The era is most famous for theatre, as William Shakespeare and many others composed plays that broke free of England's past style of theatre. It was an age of exploration and expansion abroad, while back at home, the Protestant Reformation became more acceptable to the people, most certainly after the Spanish Armada was repulsed. It was also the end of the period when England was a separate realm before its royal union with Scotland.

The Elizabethan age contrasts sharply with the previous and following reigns. It was a brief period of internal peace between the English Reformation and the religious battles between Protestants and Catholics and then the political battles between parliament and the monarchy that engulfed the remainder of the seventeenth century. The Protestant/Catholic divide was settled, for a time, by the Elizabethan Religious Settlement, and parliament was not yet strong enough to challenge royal absolutism.

England was also well-off compared to the other nations of Europe. The Italian Renaissance had come to an end under the weight of Spanish domination of the peninsula. France was embroiled in its own religious battles that were (temporarily) settled in 1598 by a policy of tolerating Protestantism with the Edict of Nantes. In part because of this, but also because the English had been expelled from their last outposts on the continent by Spain's tercios, the centuries-long conflict between France and England was largely suspended for most of Elizabeth's reign.

The one great rival was Spain, with whom England clashed both in Europe and the Americas in skirmishes that exploded into the Anglo-Spanish War of 1585–1604. An attempt by Philip II of Spain to invade England with the Spanish Armada in 1588 was famously defeated, but the tide of war turned against England with an unsuccessful expedition to Portugal and the Azores, the Drake-Norris Expedition of 1589. Thereafter, Spain provided some support for Irish Catholics in a debilitating rebellion against English rule, and Spanish naval and land forces inflicted a series of reversals against English offensives. This drained both the English Exchequer and economy that had been so carefully restored under Elizabeth's prudent guidance. English commercial and territorial expansion would be limited until the signing of the Treaty of London the year following Elizabeth's death.

England during this period had a centralised, well-organised, and effective government, largely a result of the reforms of Henry VII and Henry VIII, as well as Elizabeth's harsh punishments for any dissenters. Economically, the country began to benefit greatly from the new era of trans-Atlantic trade and persistent theft of Spanish treasure.

Heisei period

The Heisei period (Japanese: 平成時代, Hepburn: Heisei jidai) is the current era in Japan. The Heisei period started on 8 January 1989, the day after the death of the Emperor Hirohito, when his son, Akihito, acceded to the throne as the 125th Emperor. In accordance with Japanese customs, Hirohito was posthumously renamed "Emperor Shōwa" on 31 January 1989.

Thus, 1989 corresponds to Shōwa 64 until 7 January, and Heisei 1 (平成元年, Heisei gannen, gannen means "first year") from 8 January. To convert a Gregorian calendar year (1989–2019) to Heisei, 1989 needs to be subtracted from the year in question, then 1 added (e.g. 2019 in Heisei: 2019-1989+1=31; so 2019=Heisei 31).

The Heisei period will likely end on 30 April 2019 (Heisei 31), the date on which Emperor Akihito is expected to abdicate the Chrysanthemum Throne.


Japan (Japanese: 日本; Nippon [ɲippoɴ] or Nihon [ɲihoɴ]; formally 日本国 Nippon-koku or Nihon-koku, lit. "State of Japan") is an island country in East Asia. Located in the Pacific Ocean, it lies off the eastern coast of the Asian continent and stretches from the Sea of Okhotsk in the north to the East China Sea and the Philippine Sea in the south.

The kanji that make up Japan's name mean "sun origin", and it is often called the "Land of the Rising Sun". Japan is a stratovolcanic archipelago consisting of about 6,852 islands. The four largest are Honshu, Hokkaido, Kyushu, and Shikoku, which make up about ninety-seven percent of Japan's land area and often are referred to as home islands. The country is divided into 47 prefectures in eight regions, with Hokkaido being the northernmost prefecture and Okinawa being the southernmost one. The population of 127 million is the world's tenth largest, of which 98.5% are ethnic Japanese. 90.7% of people live in cities, while 9.3% live in the countryside. About 13.8 million people live in Tokyo, the capital of Japan. The Greater Tokyo Area is the most populous metropolitan area in the world with over 38 million people.Archaeological research indicates that Japan was inhabited as early as the Upper Paleolithic period. The first written mention of Japan is in Chinese history texts from the 1st century AD. Influence from other regions, mainly China, followed by periods of isolation, particularly from Western Europe, has characterized Japan's history.

From the 12th century until 1868, Japan was ruled by successive feudal military shōguns who ruled in the name of the Emperor. Japan entered into a long period of isolation in the early 17th century, which was ended in 1853 when a United States fleet pressured Japan to open to the West. After nearly two decades of internal conflict and insurrection, the Imperial Court regained its political power in 1868 through the help of several clans from Chōshū and Satsuma – and the Empire of Japan was established. In the late 19th and early 20th centuries, victories in the First Sino-Japanese War, the Russo-Japanese War and World War I allowed Japan to expand its empire during a period of increasing militarism. The Second Sino-Japanese War of 1937 expanded into part of World War II in 1941, which came to an end in 1945 following the Japanese surrender. Since adopting its revised constitution on May 3, 1947, during the occupation led by SCAP, the sovereign state of Japan has maintained a unitary parliamentary constitutional monarchy with an Emperor and an elected legislature called the National Diet.

Japan is a member of the ASEAN Plus mechanism, UN, the OECD, the G7, the G8, and the G20, and is considered a great power. Its economy is the world's third-largest by nominal GDP and the fourth-largest by purchasing power parity. It is also the world's fourth-largest exporter and fourth-largest importer.

Japan benefits from a highly skilled and educated workforce; it has among the world's largest proportion of citizens holding a tertiary education degree. Although it has officially renounced its right to declare war, Japan maintains a modern military with the world's eighth-largest military budget, used for self-defense and peacekeeping roles; it ranked as the world's fourth most-powerful military in 2015. Japan is a highly developed country with a very high standard of living and Human Development Index. Its population enjoys the highest life expectancy and third lowest infant mortality rate in the world, but is experiencing issues due to an aging population and low birthrate. Japan is renowned for its historical and extensive cinema, influential music industry, anime, video gaming, rich cuisine and its major contributions to science and modern technology.

Jim Crow laws

Jim Crow laws were state and local laws that enforced racial segregation in the Southern United States. All were enacted in the late 19th and early 20th centuries by white Democratic-dominated state legislatures after the Reconstruction period. The laws were enforced until 1965. In practice, Jim Crow laws mandated racial segregation in all public facilities in the states of the former Confederate States of America, starting in the 1870s and 1880s, and were upheld in 1896, by the U.S. Supreme Court's "separate but equal" legal doctrine for facilities for African Americans, established with the court's decision in the case of Plessy vs. Ferguson. Moreover, public education had essentially been segregated since its establishment in most of the South, after the Civil War (1861–65).

The legal principle of "separate, but equal" racial segregation was extended to public facilities and transportation, including the coaches of interstate trains and buses. Facilities for African Americans and Native Americans were consistently inferior and underfunded, compared to the facilities for white Americans; sometimes there were no facilities for people of color. As a body of law, Jim Crow institutionalized economic, educational, and social disadvantages for African Americans, and other people of color living in the south. Legalized racial segregation principally existed in the Southern states, while Northern and Western racial segregation generally was a matter of fact — enforced in housing with private covenants in leases, bank lending-practices, and employment-preference discrimination, including labor-union practices.

Jim Crow laws—sometimes, as in Florida, part of state constitutions—mandated the segregation of public schools, public places, and public transportation, and the segregation of restrooms, restaurants, and drinking fountains for whites and blacks. The U.S. military was already segregated. President Woodrow Wilson, a Southern Democrat, initiated segregation of federal workplaces in 1913.These Jim Crow laws revived principles of the 1865 and 1866 Black Codes, which had previously restricted the civil rights and civil liberties of African Americans. Segregation of public (state-sponsored) schools was declared unconstitutional by the Supreme Court of the United States in 1954 in Brown v. Board of Education. In some states it took many years to implement this decision. Generally, the remaining Jim Crow laws were overruled by the Civil Rights Act of 1964 and the Voting Rights Act of 1965, but years of action and court challenges have been needed to unravel the many means of institutional discrimination.


The Jurassic (; from Jura Mountains) was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions.

The Jurassic period is divided into three epochs: Early, Middle, and Late. Similarly, in stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, and Upper Jurassic series of rock formations.

The Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified.

By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests.

On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.


The Mesozoic Era ( or ) is an interval of geological time from about 252 to 66 million years ago. It is also called the Age of Reptiles, a phrase introduced by the 19th century paleontologist Gideon Mantell who viewed it as dominated by diapsids such as Iguanodon, Megalosaurus, Plesiosaurus and Pterodactylus. To paleobotanists, this Era is also called the Age of Conifers.Mesozoic means "middle life", deriving from the Greek prefix meso-/μεσο- for "between" and zōon/ζῷον meaning "animal" or "living being". The name "Mesozoic" was proposed in 1840 by the British geologist John Phillips (1800–1874). It is one of three geologic eras of the Phanerozoic Eon, preceded by the Paleozoic ("ancient life") and succeeded by the Cenozoic ("new life"). The era is subdivided into three major periods: the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs and stages.

The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction whose victims included the non-avian dinosaurs. The Mesozoic was a time of significant tectonic, climate and evolutionary activity. The era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would move into their current positions during the next era. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Dinosaurs first appeared in the Mid-Triassic, and became the dominant terrestrial vertebrates in the Late Triassic or Early Jurassic, occupying this position for about 150 or 135 million years until their demise at the end of the Cretaceous. Birds first appeared in the Jurassic (however, true toothless birds appeared first in the Cretaceous), having evolved from a branch of theropod dinosaurs. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic.

Mughal Empire

The Mughal Empire (Persian: گورکانیان‬‎, translit. Gūrkāniyān; Urdu: مغلیہ سلطنت‬‎, translit. Mughliyah Saltanat) or Mogul Empire was an empire in the Indian subcontinent, founded in 1526. It was established and ruled by the Timurid dynasty, with Turco-Mongol Chagatai roots from Central Asia, claiming direct descent from both Genghis Khan (through his son Chagatai Khan) and Timur, and with significant Indian Rajput and Persian ancestry through marriage alliances; the first two Mughal emperors had both parents from Central Asian ancestry. The dynasty was Indo-Persian in culture, combining Persianate culture with local Indian cultural influences visible in its traits and customs.The beginning of the empire is conventionally dated to the victory by its founder Babur over Ibrahim Lodi, the last ruler of the Delhi Sultanate, in the First Battle of Panipat (1526). During the reign of Humayun, the successor of Babur, the empire was briefly interrupted by the Sur Empire. The "classic period" of the Mughal Empire started in 1556 with the ascension of Akbar the Great to the throne. Some Rajput kingdoms continued to pose a significant threat to the Mughal dominance of northwestern India, but most of them were subdued by Akbar. All Mughal emperors were Muslims; Akbar, however, propounded a syncretic religion in the latter part of his life called Dīn-i Ilāhī, as recorded in historical books like Ain-i-Akbari and Dabistān-i Mazāhib. The Mughal Empire did not try to intervene in the local societies during most of its existence, but rather balanced and pacified them through new administrative practices and diverse and inclusive ruling elites, leading to more systematic, centralised, and uniform rule. Traditional and newly coherent social groups in northern and western India, such as the Marathas, the Rajputs, the Pashtuns, the Hindu Jats and the Sikhs, gained military and governing ambitions during Mughal rule, which, through collaboration or adversity, gave them both recognition and military experience.Internal dissatisfaction arose due to the weakness of the empire's administrative and economic systems, leading to its break-up and declarations of independence of its former provinces by the Nawab of Bengal, the Nawab of Awadh, the Nizam of Hyderabad and other small states. In 1739, the Mughals were crushingly defeated in the Battle of Karnal by the forces of Nader Shah, the founder of the Afsharid dynasty in Persia, and Delhi was sacked and looted, drastically accelerating their decline. By the mid-18th century, the Marathas had routed Mughal armies and won over several Mughal provinces from the Punjab to Bengal. During the following century Mughal power had become severely limited, and the last emperor, Bahadur Shah II, had authority over only the city of Shahjahanabad. During the Indian Rebellion of 1857 against the British, Bahadur issued a firman supporting the Indian Rebellion of 1857. Consequent to the rebellion's defeat he was tried by the British East India Company for treason, imprisoned, and exiled to Rangoon. The last remnants of the empire were formally taken over by the British, and the British Parliament passed the Government of India Act 1858 to enable the Crown formally to displace the rights of the East India Company and assume direct control of India in the form of the new British Raj.

The Mughal Empire at its peak extended over nearly all of the Indian subcontinent and parts of Afghanistan. It was the third largest empire to have existed in the Indian subcontinent (behind the Maurya Empire, and the British Indian Empire which replaced it), spanning approximately four million square kilometres at its zenith, second to the Maurya Empire. The maximum expansion was reached during the reign of Aurangzeb, who ruled over more than 150 million subjects, nearly one quarter of the world's population at the time. The Mughal Empire also ushered in a period of proto-industrialization, and around the 17th century, Mughal India became the world's largest economic and manufacturing power, producing a quarter of global industrial output up until the 18th century. The Mughal Empire is considered "India's last golden age" and one of the three Islamic Gunpowder Empires (along with the Ottoman Empire and Safavid Persia). The reign of Shah Jahan, the fifth emperor, between 1628 and 1658, was the zenith of Mughal architecture with famous monuments such as the Taj Mahal and Moti Masjid at Agra, the Red Fort, the Jama Masjid, Delhi, and the Lahore Fort.


The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago (Mya), to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the following Triassic period belongs to the Mesozoic era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm.

The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs, and archosaurs. The world at the time was dominated by two continents known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors.

The Permian (along with the Paleozoic) ended with the Permian–Triassic extinction event, the largest mass extinction in Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out. It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; on land, ecosystems took 30 million years to recover.


The Precambrian (or Pre-Cambrian, sometimes abbreviated pЄ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.

The Precambrian (colored green in the timeline figure) is an informal unit of geologic time, subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago (Ga) to the beginning of the Cambrian Period, about 541 million years ago (Ma), when hard-shelled creatures first appeared in abundance.

Progressive Era

The Progressive Era was a period of widespread social activism and political reform across the United States that spanned from the 1890s to the 1920s. The main objectives of the Progressive movement were eliminating problems caused by industrialization, urbanization, immigration, and political corruption. The movement primarily targeted political machines and their bosses. By taking down these corrupt representatives in office, a further means of direct democracy would be established. They also sought regulation of monopolies (trust busting) and corporations through antitrust laws, which were seen as a way to promote equal competition for the advantage of legitimate competitors.

Many progressives supported prohibition of alcoholic beverages, ostensibly to destroy the political power of local bosses based in saloons, but others out of a religious motivation. At the same time, women's suffrage was promoted to bring a "purer" female vote into the arena. A third theme was building an Efficiency Movement in every sector that could identify old ways that needed modernizing, and bring to bear scientific, medical and engineering solutions; a key part of the efficiency movement was scientific management, or "Taylorism". The middle class was in charge for helping reform the Progressive Era, and they got stuck with all of the burdens of this reformation. In Michael McGerr's book A Fierce Discontent, Jane Addams stated that she believed in the necessity of "association" of stepping across the social boundaries of industrial America.Many activists joined efforts to reform local government, public education, medicine, finance, insurance, industry, railroads, churches, and many other areas. Progressives transformed, professionalized and made "scientific" the social sciences, especially history, economics, and political science. In academic fields the day of the amateur author gave way to the research professor who published in the new scholarly journals and presses. The national political leaders included Republicans Theodore Roosevelt, Robert M. La Follette Sr., and Charles Evans Hughes and Democrats William Jennings Bryan, Woodrow Wilson and Al Smith. Leaders of the movement also existed far from presidential politics: Jane Addams, Grace Abbott, Edith Abbott and Sophonisba Breckinridge were among the most influential non-governmental Progressive Era reformers.

Initially the movement operated chiefly at local level, but later it expanded to state and national levels. Progressives drew support from the middle class, and supporters included many lawyers, teachers, physicians, ministers, and business people. Some Progressives strongly supported scientific methods as applied to economics, government, industry, finance, medicine, schooling, theology, education, and even the family. They closely followed advances underway at the time in Western Europe and adopted numerous policies, such as a major transformation of the banking system by creating the Federal Reserve System in 1913 and the arrival of cooperative banking in the US with the founding of the first credit union in 1908. Reformers felt that old-fashioned ways meant waste and inefficiency, and eagerly sought out the "one best system".

Prohibition in the United States

Prohibition in the United States was a nationwide constitutional ban on the production, importation, transportation, and sale of alcoholic beverages from 1920 to 1933.

During the nineteenth century, alcoholism, family violence, and saloon-based political corruption prompted prohibitionists, led by pietistic Protestants, to end the alcoholic beverage trade to cure the ill society and weaken the political opposition. One result was that many communities in the late-nineteenth and early-twentieth centuries introduced alcohol prohibition, with the subsequent enforcement in law becoming a hotly debated issue. Prohibition supporters, called "drys", presented it as a victory for public morals and health.

Promoted by the "dry" crusaders, the movement was led by pietistic Protestants and social Progressives in the Prohibition, Democratic, and Republican parties. It gained a national grass roots base through the Woman's Christian Temperance Union. After 1900, it was coordinated by the Anti-Saloon League. Opposition from the beer industry mobilized "wet" supporters from the Catholic and German Lutheran communities. They had funding to fight back, but by 1917–18 the German community had been marginalized by the nation's war against Germany, and the brewing industry was shut down in state after state by the legislatures and finally nationwide under the Eighteenth Amendment to the United States Constitution in 1920. Enabling legislation, known as the Volstead Act, set down the rules for enforcing the federal ban and defined the types of alcoholic beverages that were prohibited. For example, religious use of wine was allowed. Private ownership and consumption of alcohol were not made illegal under federal law, but local laws were stricter in many areas, with some states banning possession outright.

Criminal gangs were able to gain control of the beer and liquor supply for many cities. By the late-1920s a new opposition mobilized nationwide. Wets attacked prohibition as causing crime, lowering local revenues, and imposing "rural" Protestant religious values on "urban" United States. Prohibition ended with the ratification of the Twenty-first Amendment, which repealed the Eighteenth Amendment on December 5, 1933. Some states continued statewide prohibition, marking one of the last stages of the Progressive Era.

Research shows that prohibition reduced overall alcohol consumption by half during the 1920s, and consumption remained below pre-Prohibition levels until the 1940s, suggesting that Prohibition did socialize a significant proportion of the population in temperate habits, at least temporarily. Rates of liver cirrhosis "fell by 50% early in Prohibition and recovered promptly after Repeal in 1933." Criticism remains that Prohibition led to unintended consequences such as a century of Prohibition-influenced legislation and the growth of urban crime organizations, though some scholars have argued that violent crime did not increase dramatically, while others have argued that crime during the Prohibition era was properly attributed to increased urbanization, rather than the criminalization of alcohol use. As an experiment it lost supporters every year, and lost tax revenue that governments needed when the Great Depression began in 1929.

Reconstruction era

The Reconstruction era was the period from 1863 to 1877 in American history. The term has two applications: the first applies to the complete history of the entire country from 1865 to 1877 following the American Civil War; the second, to the attempted transformation of the 11 ex-Confederate states from 1863 to 1877, as directed by Congress. Reconstruction ended the remnants of Confederate secession and ended slavery, making the newly-free slaves citizens with civil rights apparently guaranteed by three new Constitutional amendments. Three visions of Civil War memory appeared during Reconstruction: the reconciliationist vision, which was rooted in coping with the death and devastation the war had brought; the white supremacist vision, which included terror and violence; and the emancipationist vision, which sought full freedom, citizenship, and Constitutional equality for African Americans.Presidents Abraham Lincoln and Andrew Johnson both took moderate positions designed to bring the South back into the Union as quickly as possible, while Radical Republicans in Congress sought stronger measures to upgrade the rights of African Americans, including the Fourteenth Amendment to the United States Constitution, while curtailing the rights of former Confederates, such as through the provisions of the Wade–Davis Bill. Johnson, a former Tennessee Senator, former slave owner, and the most prominent Southerner to oppose the Confederacy, followed a lenient policy toward ex-Confederates. Lincoln's last speeches show that he was leaning toward supporting the enfranchisement of all freedmen, whereas Johnson was opposed to this.Johnson's interpretations of Lincoln's policies prevailed until the Congressional elections of 1866. Those elections followed outbreaks of violence against blacks in the former rebel states, including the Memphis riots of 1866 and the New Orleans riot that same year. The subsequent 1866 election gave Republicans a majority in Congress, enabling them to pass the 14th Amendment, take control of Reconstruction policy, remove former Confederates from power, and enfranchise the freedmen. A Republican coalition came to power in nearly all the southern states and set out to transform the society by setting up a free labor economy, using the U.S. Army and the Freedmen's Bureau. The Bureau protected the legal rights of freedmen, negotiated labor contracts, and set up schools and churches for them. Thousands of Northerners came south as missionaries, teachers, businessmen and politicians. Hostile whites began referring to these politicians as "carpetbaggers". In early 1866, Congress passed the Freedmen's Bureau and Civil Rights Bills and sent them to Johnson for his signature. The first bill extended the life of the bureau, originally established as a temporary organization charged with assisting refugees and freed slaves, while the second defined all persons born in the United States as national citizens with equality before the law. After Johnson vetoed the bills, Congress overrode his veto, making the Civil Rights Act the first major bill in the history of the United States to become law through an override of a presidential veto. The Radicals in the House of Representatives, frustrated by Johnson's opposition to Congressional Reconstruction, filed impeachment charges. The action failed by one vote in the Senate. The new national reconstruction laws – in particular laws requiring suffrage (the right to vote) for freedmen – incensed white supremacists in the south, giving rise to the Ku Klux Klan. During 1867-69 the Klan murdered Republicans and outspoken freedmen in the south, including Arkansas Congressman James M. Hinds.

Elected in 1868, Republican President Ulysses S. Grant supported Congressional Reconstruction and enforced the protection of African Americans in the South through the use of the Enforcement Acts passed by Congress. Grant used the Enforcement Acts to effectively combat the Ku Klux Klan, which was essentially wiped out, although a new incarnation of the Klan eventually would again come to national prominence in the 1920s. Nevertheless, President Grant was unable to resolve the escalating tensions inside the Republican Party between the northerners on the one hand, and those Republicans originally hailing from the South on the other (this latter group would be labelled "Scalawags" by those opposing Reconstruction). Meanwhile, "Redeemers", self-styled Conservatives (in close cooperation with a faction of the Democratic Party) strongly opposed reconstruction. They alleged widespread corruption by the "Carpetbaggers", excessive state spending and ruinous taxes. Meanwhile, public support for Reconstruction policies, requiring continued supervision of the South, faded in the North after the Democrats, who strongly opposed Reconstruction, regained control of the House of Representatives in 1874. In 1877, as part of a Congressional bargain to elect Republican Rutherford B. Hayes as president following the close 1876 presidential election, U.S. Army troops no longer supported Republican state governments. Reconstruction was a significant chapter in the history of American civil rights. Historian Eric Foner argues:

What remains certain is that Reconstruction failed, and that for blacks its failure was a disaster whose magnitude cannot be obscured by the genuine accomplishments that did endure.

The Walt Disney Company

The Walt Disney Company, commonly known as Walt Disney or simply Disney (), (common metonym: Mouse, also Mouse House) is an American diversified multinational mass media and entertainment conglomerate headquartered at the Walt Disney Studios in Burbank, California. It is the world's largest independent media conglomerate in terms of revenue, ahead of NBCUniversal and WarnerMedia, which are owned by telecommunications giants Comcast and AT&T respectively.The company was founded on October 16, 1923 by brothers Walt and Roy O. Disney as the Disney Brothers Cartoon Studio; it also operated under the names The Walt Disney Studio and Walt Disney Productions before officially changing its name to The Walt Disney Company in 1986. The company established itself as a leader in the American animation industry before diversifying into live-action film production, television, and theme parks.

Since the 1980s, Disney has created and acquired corporate divisions in order to market more mature content than is typically associated with its flagship family-oriented brands. The company is known for its film studio The Walt Disney Studios, which is one of the largest and best-known studios in American cinema. Disney's other main divisions are Disney Parks, Experiences and Products, Disney Media Networks, and Walt Disney Direct-to-Consumer and International. Disney also owns and operates the ABC broadcast network; cable television networks such as Disney Channel, ESPN, A&E Networks, and Freeform; publishing, merchandising, music, and theater divisions; and Walt Disney Parks and Resorts, a group of 14 theme parks around the world. The company has been a component of the Dow Jones Industrial Average since 1991. Mickey Mouse was created in 1928 and is the signature mascot and emblem for Disney and one of the world's most recognizable characters.On December 14, 2017, Disney announced an agreement to acquire 21st Century Fox for $52 billion. The bid was later increased to $71 billion on June 20, 2018 in the wake of Comcast's $65 billion bid for Fox. The acquisition will lead to the formation of a new company, which will keep The Walt Disney Company name.


The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Therapsids and archosaurs were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period.The first true mammals, themselves a specialized subgroup of therapsids, also evolved during this period, as well as the first flying vertebrates, the pterosaurs, who, like the dinosaurs, were a specialized subgroup of archosaurs. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south.

The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event, that wiped out many groups and allowed dinosaurs to assume dominance in the Jurassic.

The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers (tri meaning "three") that are found throughout Germany and northwestern Europe—red beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstones—called the "Trias".

Victorian era

In the history of the United Kingdom, the Victorian era was the period of Queen Victoria's reign, from 20 June 1837 until her death on 22 January 1901. The era followed the Georgian period and preceded the Edwardian period, and its later half overlaps with the first part of the Belle Époque era of Continental Europe. In terms of moral sensibilities and political reforms, this period began with the passage of the Reform Act 1832. There was a strong religious drive for higher moral standards led by the nonconformist churches, such as the Methodist, and the Evangelical wing of the established Church of England. Britain's relations with the other Great Powers were driven by the colonial antagonism of the Great Game with Russia, climaxing during the Crimean War; a Pax Britannica of international free trade was maintained by the country's naval and industrial supremacy. Britain embarked on global imperial expansion, particularly in Asia and Africa, which made the British Empire the largest empire in history. National self-confidence peaked.Ideologically, the Victorian era witnessed resistance to the rationalism that defined the Georgian period and an increasing turn towards romanticism and even mysticism with regard to religion, social values, and arts.Domestically, the political agenda was increasingly liberal, with a number of shifts in the direction of gradual political reform, industrial reform, and the widening of the franchise. There were unprecedented demographic changes: the population of England and Wales almost doubled from 16.8 million in 1851 to 30.5 million in 1901, and Scotland's population also rose rapidly, from 2.8 million in 1851 to 4.4 million in 1901. However, Ireland's population decreased sharply, from 8.2 million in 1841 to less than 4.5 million in 1901, mostly due to emigration and the Great Famine. Between 1837 and 1901 about 15 million emigrated from Great Britain, mostly to the United States, Canada, South Africa, New Zealand, and Australia.The two main political parties during the era remained the Whigs/Liberals and the Conservatives; by its end, the Labour Party had formed as a distinct political entity. These parties were led by such prominent statesmen as Lord Melbourne, Sir Robert Peel, Lord Derby, Lord Palmerston, Benjamin Disraeli, William Gladstone, and Lord Salisbury. The unsolved problems relating to Irish Home Rule played a great part in politics in the later Victorian era, particularly in view of Gladstone's determination to achieve a political settlement in Ireland.

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