Anno Domini in the context of 801

The emperor of Japan is the hereditary monarch and head of state of Japan. The emperor is defined by the Constitution of Japan as the symbol of the Japanese state and the unity of the Japanese people, his position deriving from "the will of the people with whom resides sovereign power". The Imperial Household Law governs the line of imperial succession. Pursuant to his constitutional role as a national symbol, and in accordance with rulings by the Supreme Court of Japan, the emperor is personally immune from prosecution. By virtue of his position as the head of the Imperial House, the emperor is also recognized as the head of the Shinto religion, which holds him to be the direct descendant of the sun goddess Amaterasu. According to tradition, the office of emperor was created in the 7th century BC, but the first historically verifiable emperors appear around the 5th or 6th centuries AD.

The role of the emperor of Japan has historically alternated between a largely ceremonial symbolic role and that of an actual imperial ruler. Since the establishment of the first shogunate in 1192, the emperors of Japan have rarely taken on a role as supreme battlefield commander, unlike many Western monarchs. Japanese emperors have nearly always been controlled by external political forces, to varying degrees. Between 1192 and 1867, the shōguns, or their shikken regents in Kamakura (1203–1333), were the de facto rulers of Japan, although they were nominally appointed by the emperor. After the Meiji Restoration in 1868, the emperor was the embodiment of all sovereign power in the realm, as enshrined in the Meiji Constitution of 1889. Since the enactment of the 1947 constitution, the role of emperor has been relegated to that of a ceremonial head of state without even nominal political powers. The emperor is the head of the Japanese honors system, conferring orders, decorations, medals, and awards in the name of the state and on behalf of its people in accordance with the advice of the Cabinet.

Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian or Julian calendar, and are exactly equivalent to the Anno Domini (AD) and Before Christ (BC) notations. The expressions "2025 CE" and "AD 2025" each equally describe the current year; "400 BCE" and "400 BC" are the same year too. BCE/CE are primarily used to avoid religious connotations, by not referring to Jesus as Dominus [Lord].

The Stone Age was a broad prehistoric period during which stone was widely used to make stone tools with an edge, a point, or a percussion surface. The period lasted for roughly 3.4 million years and ended between 4000 BC and 2000 BC, with the advent of metalworking. Because of its enormous timescale, it encompasses 99% of human history.

Though some simple metalworking of malleable metals, particularly the use of gold and copper for purposes of ornamentation, was known in the Stone Age, it is the melting and smelting of copper that marks the end of the Stone Age. In Western Asia, this occurred by about 3000 BC, when bronze became widespread. The term Bronze Age is used to describe the period that followed the Stone Age, as well as to describe cultures that had developed techniques and technologies for working copper alloys (bronze: originally copper and arsenic, later copper and tin) into tools, supplanting stone in many uses.

The Varronian chronology is the commonly accepted chronology of early Roman history named after the Roman antiquarian Marcus Terentius Varro. It is from this chronology that the commonly used dates for the foundation of the city (753 BC), the overthrow of the monarchy (509 BC), the Decimvirates (451–450 BC), the Gallic sack of Rome (390 BC), and the first plebeian consul (366 BC) are derived. The chronology consists of an ordered list of magisterial colleges (eg pairs of consuls) which, in modern times, are regularly assigned to years BC.

The years given by the Varronian chronology prior to 300 BC should not be accepted as absolute dates. Years in the chronology are also demonstrably incorrect and it flows four years prior to actual events by 340 BC. Moreover, Roman historians and antiquarians (most especially Livy and Dionysius of Halicarnassus) also did not all use Varro's scheme. Because both the ordering and absolute position of Varronian years is not well established for this early period, the numeric years derived from it should be taken as "no more than numerical symbols for specific consular years".

The Roman architectural revolution, also known as the concrete revolution, is the name sometimes given to the widespread use in Roman architecture of the previously little-used architectural forms of the arch, vault, and dome. For the first time in Europe, possibly in the world (earlier experiments with arches in Ancient Egypt and Mesopotamia notwithstanding), the potential of these elements was fully appreciated and exploited in the construction of a wide range of civil engineering structures, public buildings, and military facilities. Throughout the Roman Empire, from Syria to Scotland, engineers erected structures using semicircular arches. The first use of arches was for civic structures, like drains and city gates. Later the arches were utilized for major civic buildings bridges and aqueducts, with the outstanding 1st century AD examples provided by the Colosseum, Pont Du Gard, and the aqueduct of Segovia. The introduction of the ceremonial triumphal arch dates back to Roman Republic, although the best examples are from the imperial times (Arch of Augustus at Susa, Arch of Titus).

A crucial factor in this development that saw a trend to monumental architecture was the invention of Roman concrete (also called opus caementicium), which led to the liberation of the shape from the dictate of the traditional materials of stone and brick.

The Sasanian Empire (/səˈsɑːniən/), officially Eranshahr (Middle Persian: 𐭠𐭩𐭥𐭠𐭭𐭱𐭲𐭥𐭩 Ērānšahr, "Empire of the Iranians"), was an Iranian empire that was founded and ruled by the House of Sasan from 224 to 651 AD. Lasting for over four centuries, the length of the Sasanian dynasty's reign over ancient Iran was second only to that of the Arsacid dynasty of Parthia which immediately preceded it.

Founded by Ardashir I, whose rise coincided with the decline of Arsacid influence in the face of both internal and external strife, the House of Sasan was highly determined to restore the legacy of the Achaemenid Empire by expanding and consolidating the dominions of the Iranian nation. Most notably, after defeating Artabanus IV of Parthia at the Battle of Hormozdgan in 224, it began competing far more zealously with the neighbouring Roman Empire than the Arsacids had, thus sparking a new phase of the Roman–Iranian Wars. These efforts by Sasanian rulers ultimately led to the re-establishment of Iran as a major power of late antiquity.

Bulgarian Battle of Versinikia (Bulgarian: Битката при Версиникия; Greek: Μάχη της Βερσινικίας) was a battle fought in 813 AD between the Byzantine Empire and the Bulgarian Empire, near the city of Adrianople (Edirne), in modern-day Turkey.

The Bulgarian army, led by Krum of Bulgaria, defeated the Byzantine forces. Following this defeat, Michael I Rangabe abdicated, with Leo V the Armenian taking the Byzantine throne. The battle further strengthened Bulgarian control in the region after their victory over Nikephoros I two years earlier. After the battle, the Bulgarians controlled the whole region of Eastern Thrace (until the Byzantine–Bulgarian Treaty of 815), with the exception of a few castles that remained in Byzantine control. Krum died on 13 April 814, but his muster of "5,000 iron-plated wagons [ . . . ] to carry the siege equipment" alarmed the Byzantine court to such an effect that they asked for the aid of the Carolingian Emperor Louis the Pious. These large-scale military preparations were Krum's attempt to avenge his failure at the Second Bulgarian Siege of Constantinople one year prior.

Byzantine Anatolia refers to the peninsula of Anatolia (located in present-day Turkey) during the rule of the Byzantine Empire. Anatolia was of vital importance to the empire following the Muslim invasion of Syria and Egypt during the reign of the Byzantine Emperor Heraclius in the years 634–645 AD. Over the next two hundred and fifty years, the region suffered constant raids by Arab Muslim forces raiding mainly from the cities of Antioch, Tarsus, and Aleppo near the Anatolian borders. However, the Byzantine Empire maintained control over the Anatolian peninsula until the High Middle Ages (years 1080s), when imperial authority in the area began to collapse.

The Byzantine Empire re-established control over parts of Anatolia during the First Crusade, and following the sack of Constantinople during the Fourth Crusade, Anatolia became the heartland of the successor states of the Empire of Nicaea and Empire of Trebizond. Following the retaking of Constantinople in 1261, the region gradually passed out of Byzantine control and into the hands of the Ottoman Turks as the empire gradually crumbled. The last Byzantine fortress of Philadelphia fell in 1399, and the last Byzantine presence in the area at Trapezus ended in 1461 with the fall of Trebizond.

The Kingdom of Georgia (Georgian: საქართველოს სამეფო, romanized: Sakartvelos samepo), also known as the Georgian Empire, was a medieval Eurasian monarchy that was founded in c. 1008 AD. It reached its Golden Age of political and economic strength during the reign of King David IV and Queen Tamar the Great from the 11th to 13th centuries. Georgia became one of the pre-eminent nations of the Christian East, and its pan-Caucasian empire and network of tributaries stretched from Eastern Europe to Anatolia and northern frontiers of Iran, while Georgia also maintained religious possessions abroad, such as the Monastery of the Cross in Jerusalem and the Monastery of Iviron in Greece. It is the principal historical precursor of present-day Georgia.

Kingdom of Georgia emerged in the early 11th century out of unification of various Georgian kingdoms, most notably the Kingdom of the Iberians and the Kingdom of Abkhazia. Lasting for nearly five centuries, the kingdom fell to the Mongol invasions in the 13th century, but managed to re-assert sovereignty by the 1340s. The following decades were marked by the Black Death, as well as numerous invasions under the leadership of Timur, who devastated the country's economy, population, and urban centers. The Kingdom's geopolitical situation further worsened after the conquest of the Byzantine Empire and the Empire of Trebizond by the Ottoman Turks. As a result of these processes, by the end of the 15th century Georgia turned into a fractured entity. This whole series of events also led to the final collapse of the kingdom into anarchy by 1466 and the mutual recognition of its constituent kingdoms of Kartli, Kakheti, and Imereti as independent states between 1490 and 1493—each led by a rival branch of the Bagrationi dynasty, and into five semi-independent principalities—Odishi, Guria, Abkhazia, Svaneti, and Samtskhe.

Tbilisi (/təbɪˈliːsi, təˈbɪlɪsi/ tə-bil-EE-see, tə-BIL-iss-ee; Georgian: თბილისი, pronounced [ˈtʰbilisi] ), Georgian: ტფილისი, romanized: t'pilisi [tʼpʰilisi]) is the capital and largest city of Georgia, located on the banks of the Kura River. With more than 1.3 million inhabitants, it contains almost one third of the country's population. Tbilisi was founded in the fifth century AD by Vakhtang I of Iberia and has since served as the capital of various Georgian kingdoms and republics. Between 1801 and 1917, then part of the Russian Empire, it was the seat of the Caucasus Viceroyalty, governing both the northern and the southern sides of the Caucasus.

Because of its location at the crossroads between Europe and Asia, and its proximity to the lucrative Silk Road, throughout history, Tbilisi has been a point of contention among various global powers. To this day, the city's location ensures its position as an important transit route for energy and trade projects. Tbilisi's history is reflected in its architecture, which is a mix of medieval, neoclassical, Beaux Arts, Art Nouveau, Stalinist, and Modern structures.

The history of timekeeping devices dates back to when ancient civilizations first observed astronomical bodies as they moved across the sky. Devices and methods for keeping time have gradually improved through a series of new inventions, starting with measuring time by continuous processes, such as the flow of liquid in water clocks, to mechanical clocks, and eventually repetitive, oscillatory processes, such as the swing of pendulums. Oscillating timekeepers are used in modern timepieces. Sundials and water clocks were first used in ancient Egypt c. 1200 BC and later by the Babylonians, the Greeks and the Chinese. Incense clocks were being used in China by the 6th century. In the medieval period, Islamic water clocks were unrivalled in their sophistication until the mid-14th century. The hourglass, invented in Europe, was one of the few reliable methods of measuring time at sea.

In medieval Europe, purely mechanical clocks were developed after the invention of the bell-striking alarm, used to signal the correct time to ring monastic bells. The weight-driven mechanical clock controlled by the action of a verge and foliot was a synthesis of earlier ideas from European and Islamic science. Mechanical clocks were a major breakthrough, one notably designed and built by Henry de Vick in c. 1360, which established basic clock design for the next 300 years. Minor developments were added, such as the invention of the mainspring in the early 15th century, which allowed small clocks to be built for the first time.

Year 404 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Volusus, Cossus, Fidenas, Ambustus, Maluginensis and Rutilus (or, less frequently, year 350 Ab urbe condita). The denomination 404 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Year 403 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Mamercinus, Varus, Potitus, Iullus, Crassus and Fusus (or, less frequently, year 351 Ab urbe condita). The denomination 403 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts of Oriental Orthodoxy as well as by the Amazigh people (also known as the Berbers). For a quick calculation, between 1901 and 2099 the much more common Gregorian date equals the Julian date plus 13 days.

The Julian calendar was proposed in 46 BC by (and takes its name from) Julius Caesar, as a reform of the earlier Roman calendar, which was largely a lunisolar one. It took effect on 1 January 45 BC, by his edict. Caesar's calendar became the predominant calendar in the Roman Empire and subsequently most of the Western world for more than 1,600 years, until 1582 when Pope Gregory XIII promulgated a revised calendar. Ancient Romans typically designated years by the names of ruling consuls; the Anno Domini system of numbering years was not devised until 525, and became widespread in Europe in the eighth century.

Trajan's Column (Italian: Colonna Traiana, Latin: Columna Traiani) is a Roman triumphal column in Rome, Italy, that commemorates Roman emperor Trajan's victory in the Dacian Wars. It was probably constructed under the supervision of the architect Apollodorus of Damascus at the order of the Roman Senate. It is located in Trajan's Forum, north of the Roman Forum. Completed in AD 113, the freestanding column is most famous for its spiral bas relief, which depicts the wars between the Romans and Dacians (101–102 and 105–106). Its design has inspired numerous victory columns, both ancient and modern.

The structure is about 30 metres (98 feet) in height, 35 metres (115 feet) including its large pedestal. The shaft is made from a series of 20 colossal Carrara marble drums, each weighing about 32 tons, with a diameter of 3.7 metres (12.1 feet). The 190-metre (620-foot) frieze winds around the shaft 23 times. Inside the shaft, a spiral staircase of 185 steps provides access to a viewing deck at the top. The capital block of Trajan's Column weighs 53.3 tons, and had to be lifted to a height of about 34 metres (112 feet). Ancient coins indicate preliminary plans to top the column with a statue of a bird, probably an eagle. After construction, a statue of Trajan was put in place; this disappeared in the Middle Ages. On December 4, 1587, the top was crowned with a bronze figure of Saint Peter the Apostle by Pope Sixtus V, which remains to this day.

Ovid, the Latin poet of the Roman Empire, was banished in 8 AD from Rome to Tomis (now Constanța, Romania) by decree of the emperor Augustus. The reasons for his banishment are uncertain. Ovid's exile is related by the poet himself, and also in brief references to the event by Pliny the Elder and Statius. At the time, Tomis was a remote town on the edge of the civilized world; it was loosely under the authority of the Kingdom of Thrace (a satellite state of Rome), and was superficially Hellenized. According to Ovid, none of its citizens spoke Latin, which as an educated Roman, he found trying. Ovid wrote that the cause of his exile was carmen et error ("a poem and an error"), probably the Ars Amatoria and a personal indiscretion or mistake.

Ovid was one of the most prolific poets of his time, and before being banished had already composed his most famous poems – Heroides, Amores, Ars Amatoria, Remedia Amoris, Medicamina Faciei Femineae, his lost tragedy Medea, the ambitious Metamorphoses and the Fasti. The latter two works were left, respectively, without a final revision and only half finished. In exile, the poet continued producing works that survive today: Ibis, Tristia, Epistulae ex Ponto, and possibly several other, minor poems. These works consist of letters to friends and enemies, and also depict the poet's treatment by the Scythians – particularly the Getae, a nomadic people related to the Dacians or Thracians.

Tyrannicide or tyrannomachia is the killing or assassination of a tyrant or unjust ruler, purportedly for the common good,and usually by one of the tyrant's subjects. Tyrannicide was legally permitted and encouraged in Classical Greece. Often, the term "tyrant" was a justification for political murders by rivals, but in some exceptional cases students of Platonic philosophy risked their lives against tyrants. The killing of Clearchus of Heraclea in 353 BC by a cohort led by his own court philosopher is an example of a tyrannicide. A person who carries out a tyrannicide is also called a "tyrannicide".

The term originally denoted the action of Harmodius and Aristogeiton, who are often called the Tyrannicides, in killing Hipparchus of Athens in 514 BC.