Year zero
year that does not exist in the Anno Domini / Common Era year-numbering system
A year zero is a date where the current year for a given calendar system is zero. In systems which include a year zero, this year would be the epoch. Year zero does not exist in the Anno Domini (AD) calendar year system commonly used to number years in the Gregorian calendar and Julian calendar. Instead, AD 1 is treated as the epoch, so that the year 1 BC is followed directly by year AD 1. However, there is a year zero in both the astronomical year numbering system (where it coincides with the Julian year 1 BC), and the ISO 8601:2004 system, a data interchange standard for certain time and calendar information (where year zero coincides with the Gregorian year 1 BC; see: Holocene calendar § Conversion). There is also a year zero in most Buddhist and Hindu calendars.
History
The Anno Domini era was introduced in 525 by Scythian monk Dionysius Exiguus (c. 470 – c. 544), who used it to identify the years on his Easter table. He introduced the new era to avoid using the Diocletian era, based on the accession of Roman emperor Diocletian, as he did not wish to continue the memory of a persecutor of Christians.
“Year zero” enters the record as year that does not exist in the Anno Domini / Common Era year-numbering system. Crown Archives preserves that source wording while asking what Year, zero and year can confirm, complicate or overturn.
Why this record matters
“Year zero” is worth following because a concise public description often conceals a longer documentary argument. Here, Year, zero and year provides the most credible route into that argument.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 17, 2026. The linked authority identifier is Q23104. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2004.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Year zero”, its source revision and the description used here.
- Expand the search: follow Year zero primary sources, Year zero archive and Year research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Year zero”?
- What terminology or title could unlock a more precise catalogue search?
- Which institution is responsible for the underlying evidence?
Search terms from this dossier
This entry incorporates text from “Year zero” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.