About this site

The period from the day of accession to the day of abdication or death. Dates are used at the precision the sources support (year, month or day), and unknown parts are never filled in by guesswork, so some reigns are known to the day and others only to the year. For an emperor who was deposed and later restored, each reign is counted separately and the lengths are added.

The official histories date events by era year, lunar month and sexagenary day. The start and end of each reign were checked against the passage in the history for that emperor and converted with the calendar library sxtwl. Following historical convention, dates before October 1582 are in the Julian calendar and later dates in the Gregorian calendar. The end of a lunar year (the twelfth month, for example) can fall in the next Western year, so lunar and Western years do not always match one to one. Where sources disagree, the official history is preferred.

Dates of events such as era changes, amnesties, campaigns and rebellions are given to the month and day only in the first and last year of a reign, and otherwise to the year, so as not to claim more precision than can be checked.

Each death is classified into one of eight categories. Assassination and execution are distinguished by who did the killing: murder by someone inside the same regime (officials, members of the imperial family, eunuchs) is assassination, and a public act by the conquering side after the dynasty fell is execution. Taking one's own life under pressure from officials counts as suicide, and poisoning counts as assassination. When the sources conflict and the cause cannot be narrowed to one, it is recorded as disputed.

• Natural causes: Natural death or illness (including old age)
• Assassinated: Killed by officials, relatives, eunuchs or others within the same regime (including poisoning)
• Executed: Put to death by a hostile power, a successor regime or a conqueror, as a public act
• Killed in battle: Died in combat, whether on campaign, in defense or while suppressing a revolt
• Suicide (incl. forced): Took their own life, including when driven to it by deposition or defeat, or when ordered to do so
• Accident: Died in an accident such as a fall from a horse, drowning or fire
• Unknown: The primary sources record no cause of death or clue to it
• Disputed: Primary sources or accepted accounts conflict and cannot be narrowed to one

How each emperor came to the throne is classified from four independent questions about what the sources record: where the throne came from (inherited from the previous ruler, received from another regime, or self-proclaimed), who decided the accession (the emperor, the previous emperor, a third party, or cannot be settled from the sources), what became of the previous emperor (died, killed, abdicated, or deposed), and the blood relationship to the previous emperor. The combination gives one of eight labels.

• Designated heir: Succeeded the previous ruler of the same regime, who had chosen the heir (by testament, naming a crown prince, etc.)
• Installed by others: Succeeded the previous ruler of the same regime, but the choice was made by officials, the army, eunuchs, consort kin, an empress dowager or the imperial clan
• Usurpation: Seized the throne from the previous emperor (removing the predecessor and taking the throne were one act)
• Abdication within the dynasty: The previous emperor of the same regime handed over the throne while still alive (e.g. Emperor Xuanzong of Tang, Jiaqing Emperor, Emperor Aizong of Jin)
• Succession (circumstances unrecorded): Succeeded the previous ruler of the same regime, but the primary sources do not say who decided it (e.g. Qin Shi Huang, Emperor Taizong of Song)
• Abdication from another dynasty: Received the throne from an emperor of another family or regime in a change of dynasty led by the new emperor (e.g. Cao Pi, Yang Jian, Zhao Kuangyin)
• Self-proclaimed: Claimed the imperial title without receiving the throne from an earlier ruler (e.g. Emperor Gaozu of Han, Emperor Guangwu of Han, Hongwu Emperor)
• Proclaimed by supporters: Did not receive the throne from an earlier ruler, and did not claim it on their own initiative but was set up by others (e.g. the emperors of the Southern Ming)

“Succession (circumstances unrecorded)” is used when the history records no naming of a crown prince, no testament and no proclamation by supporters. For Qin Shi Huang, the Shiji says only 政代立為秦王; for Emperor Taizong of Song, the History of Song says only 太祖崩，帝遂即皇帝位. Even a blood heir is put in this category unless the source says the previous emperor chose them.

A founder who received the throne from the previous dynasty is classified as abdication from another dynasty, one who claimed the title on their own as self-proclaimed, and one set up by others as proclaimed by supporters. Someone who inherited a royal or military title from their forebears and only added the title of emperor (Qin Shi Huang, Emperor Zhuangzong of Later Tang, Li Yuanhao of Western Xia) is counted as a succession. An emperor who took the throne more than once is classified by the first accession.

How many times the era name was changed during the reign, counting the first era name proclaimed on accession. Emperors who reigned before era names existed (such as those of Qin) have zero.

How many empire-wide amnesties were proclaimed during the reign. Partial amnesties limited to a region or to certain offences are not counted.

How many times an empress was formally installed during the reign. Installing a new empress after deposing one, or reinstating a deposed empress, each count once. Emperors who installed no empress have zero.

How many times a crown prince (or an equivalent designated heir) was removed during the reign. Only depositions are counted, not the naming of crown princes.

How many times the emperor personally led an army to the field. Campaigns where generals were sent on the emperor's orders but the emperor stayed behind are not counted. A series of operations against the same enemy, from departure to return, counts once, even if it spans more than one year.

Rebellions suppressed counts the revolts the regime moved to put down; rebellions faced counts the revolts raised against the emperor or the regime. Both count each independent leader or uprising once, whether or not it was put down. They range from peasant revolts to armed palace coups and regicide, but exclude wars with independent powers outside the emperor's rule, foreign wars and plots that never came to an armed rising. The two usually count the same revolts from both sides, but they can differ: a reign may end before suppression begins, or a coup may be put down by someone other than the emperor's side.

How many times the main capital was formally and permanently moved during the reign. Temporary flight or tours during war, and new secondary capitals, are not counted. Several moves in a short time each count once.

All ages are in East Asian reckoning (sui), the traditional Chinese way of counting in which a person is one year old at birth and gains a year at each New Year, so the figure is one or two years higher than the Western age. Where the history gives no year of birth or age at death, the age is recorded as unknown and is not estimated, so statistics on age cover only the emperors whose ages are known.