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Regnal Years: Counting Time by Who Sat on the Throne

Most pre-modern documents date themselves by a ruler's reign, not a calendar era. Here is how king lists turn that into chronology and where the chains snap.

By Published 5 min read

Reign Creative LLC makes World History Timeline Sim, which this article links to, so we have a commercial interest in it. How we write and check articles.

Key takeaways

  • A regnal year numbers time from a ruler's accession — "year 12 of the king" — which is how the great majority of pre-modern documents date themselves.
  • King lists are the instrument that converts a pile of reigns into a chronology, by recording rulers in sequence with the length of each reign.
  • The Ashmolean's Sumerian King List is explicit about the limits of the genre: its museum description calls it a combination of myth, legend and historical information, with fantastically long reigns at the mythological end.
  • The Turin King List in the Museo Egizio is a papyrus dated to the reign of Ramesses II, and is one of the central documents for Egyptian chronology.
  • Regnal dating survived alongside calendar eras for centuries, and the Christian era itself was built by continuing a table whose years were counted from the reign of the emperor Diocletian.

A regnal year counts time from the moment a particular ruler took power: year one, year two, year twelve of that reign, then the count resets when the next ruler accedes. For most of recorded history this is how documents dated themselves. A modern reader encountering "in the fourteenth year of Emperor Kinmei" is looking at a complete, precise, locally unambiguous date — that happens to be useless without a separate body of work connecting reigns to a continuous year count.

What regnal dating is actually good at

The system suits the society that uses it. A regnal date is short, it is verifiable by anyone in the administration, it cannot drift, and it carries a political statement — the year is the king's year. Tax records, land grants, legal judgments and chronicle entries can all be filed and cross-checked without anyone needing to agree on an era epoch.

What it cannot do is span dynasties. Two documents from different reigns cannot be placed relative to each other from their dates alone. Someone has to know the order of the reigns and how long each lasted, and that knowledge lives in a separate kind of document.

King lists: the instrument that makes chronology possible

A king list records rulers in sequence with the length of each reign. Chain the reigns and you get elapsed time; anchor the chain at one end and you get calendar dates.

The Ashmolean Museum holds one of the most important examples from ancient Mesopotamia: a clay prism, each of its four sides inscribed with two columns of cuneiform recording the Sumerian language, listing a succession of cities in Sumer and neighbouring regions, their rulers, and the length of their reigns. Several versions of the Sumerian King List survive; the Ashmolean's is the most extensive and the most complete. It is dated to around 1800 BC and probably came from Larsa.

The museum's own description is admirably direct about what kind of document this is. It calls the list "not history as we would understand it, but a combination of myth, legend and historical information". It begins with the mythological origins of kingship, where individuals have fantastically long reigns, passes through the famous lines about the Flood sweeping over and kingship descending from heaven, and only becomes realistic in its reign lengths as it reaches historical rulers. It ends with King Sin-magir of the Isin dynasty, around 1827–1817 BC.

And it had a purpose. The Ashmolean notes that the list seems to have been composed to imply that dominion over Mesopotamia, determined by the gods, could be exercised by only one city at a time and only for a limited period — which conveniently made the rulers of Isin the rightful successors of earlier powerful kingdoms.

Egypt's equivalent is the Turin King List, or Royal Canon, in the Museo Egizio. It is a papyrus roughly 1.8 metres long, catalogued as Cat. 1874, dated by the museum to 1279–1213 BCE — the reign of Ramesses II, in the Nineteenth Dynasty of the New Kingdom — and acquired in the Drovetti purchase of 1842. It is a list of kings compiled centuries after many of the reigns it records, which is the ordinary situation for this genre.

Where the chains break

Four failure modes recur, and they are why early absolute dates are so often published as ranges rather than points.

  • Partial years. A reign rarely starts on New Year's Day. Whether the remainder of the outgoing ruler's year is counted to the old reign or the new one changes every downstream date by one year, and the convention is not always recoverable.
  • Overlaps. Co-rulers, contested successions and rival dynasties all produce reigns that ran simultaneously. Adding their lengths together inflates the chronology.
  • Gaps and damage. These documents survive on clay and papyrus, and damage is normal. A missing reign length does not just lose one date; it disconnects everything before it from everything after it.
  • Argument. As the Sumerian King List shows, these documents were often written to justify a claim. A compiler with a case to make may present simultaneous dynasties as consecutive ones.

Independent evidence is how the chains get checked. Excavated archives can attach a ruler to a place and a material record — UNESCO's inscription for Yin Xu, the late Shang capital near Anyang dated there to 1300–1046 BC, notes that inscriptions on oracle bones found at the site bear invaluable testimony to one of the world's oldest writing systems and to ancient beliefs and social systems. How historians date events covers the wider set of anchoring methods and how confidence varies between them.

Era names and the long survival of reign-based counting

East Asian era-name systems are a refinement of the same idea: a named period, proclaimed by the court, within which years are numbered.

The National Diet Library of Japan's account of the Japanese calendar shows the convention in use. Japan's first calendar came from China by way of Korea; in the middle of the sixth century the Yamato court invited a priest from Paekche to teach calendar-making, astronomy and geography, and Japan is reported to have organised its first calendar in the twelfth year of Suiko, which the library gives as 604. The first reference to a calendar in any Japanese record is an entry in the Nihon Shoki, Japan's oldest chronicle, dated to the sixth month of the fourteenth year of Emperor Kinmei — 553. Calendar preparation, astronomy and divination were the business of a single government office, and from the end of the tenth century the calendar passed down through the Kamo family and astronomy through the Abe family.

Regnal dating also sits inside the origin of the Christian era itself. The standard reference account of calendars records that Dionysius Exiguus built his year count by continuing an existing Easter table whose years were numbered from the beginning of the reign of the emperor Diocletian — so one regnal era was replaced by grafting a new epoch onto it. The same source notes that even after the Christian era became common in medieval ecclesiastical writing, traditional dating by regnal years continued in civil use. The arithmetic consequences of that epoch are covered in why the 1400s are the fifteenth century, and the calendars underneath in how calendars and dating systems work.

Reading reign-based dates on a timeline

A chronology app displays a calendar year, which means every regnal date it shows has already been converted by someone, with all the assumptions above baked in and invisible.

World History Timeline Sim, our own app built by Reign Creative, organises a large amount of its material by ruler and dynasty, which makes the sequence easy to browse — and that is exactly the right use for it. Treat the displayed year as a working conversion rather than a fact, especially before about 1000 BCE, and check a specific reign against a museum catalogue or an excavation report before relying on it. The app is a tool for orientation and exploration, not a substitute for textbooks, peer-reviewed scholarship or primary sources.

More on chronology and dating conventions is collected in the world history timelines hub, starting with how to actually learn something from a timeline app. Our other learning tools are listed under education and brain games.

Good to know

Frequently asked questions

What does a regnal date look like?
It names a ruler and a year within that ruler's reign — the form "in the fourteenth year of Emperor Kinmei" or "year 12 of Suiko". The National Diet Library of Japan uses exactly these forms when citing the Nihon Shoki, and supplies the modern equivalents in brackets, which is what a regnal date always needs to be useful to a modern reader.
How do historians convert a regnal year into a calendar date?
By chaining reigns together from a king list and then anchoring the chain to something independently datable — an astronomical event described in a record, a synchronism with another culture's chronology, or scientific dates from excavated material. The conversion is only as good as the weakest link in the chain, which is why absolute dates for early periods are often given as ranges.
Are king lists reliable?
They are evidence, and like all evidence they have a purpose. The Ashmolean notes that the Sumerian King List seems to have been composed to imply that rule over Mesopotamia could be exercised by only one city at a time, legitimising the rulers of Isin as successors to earlier kingdoms. A list that argues for something is still useful, provided you read it knowing what it is arguing.
Did regnal dating stop when calendar eras arrived?
Not for a long time. The standard reference account of calendars notes that even as the Christian era became common in medieval ecclesiastical writing, traditional dating by regnal years continued in civil use. Many legal and administrative systems kept reign-based citation long after a continuous year count was available for other purposes.

Sources

  1. Sumerian King List (opens in a new tab)Ashmolean Museum, University of Oxford — accessed
  2. Turin King List / Royal Canon (Cat. 1874) (opens in a new tab)Museo Egizio, Turin — accessed
  3. Calendar History 1 — The Japanese Calendar (opens in a new tab)National Diet Library, Japan — accessed
  4. Calendars and their History (opens in a new tab)NASA Goddard Space Flight Center (reprinted from the Explanatory Supplement to the Astronomical Almanac) — accessed
  5. Yin Xu (opens in a new tab)UNESCO World Heritage Centre — accessed

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