Every historical claim needs an evidence trail.

Our sourcing standard

Each published event must include at least one identifiable source supporting its date and core factual claims. A citation is a starting point rather than an automatic guarantee of accuracy. We consider who produced the source, its relationship to the event, its editorial or scholarly process, and whether independent evidence supports the same conclusion.

Preferred sources

Depending on the event and period, preferred sources may include:

• Government archives, national libraries, museums, and historical institutions.
• Universities, scholarly publishers, peer-reviewed journals, and academic reference works.
• Primary-source collections, documentary editions, laws, treaties, official records, and contemporary accounts.
• Established encyclopedias and specialist organizations with visible editorial standards.
• Reputable journalism for well-documented recent events, preferably supplemented by official or specialist sources.

Open access is helpful but does not by itself determine quality. Likewise, a prestigious publisher does not make every page equally relevant to every claim.

Primary and secondary sources

Primary sources were created during the period under study or by participants in the events. Secondary sources analyze evidence and existing scholarship. Both require critical reading. A primary source may contain propaganda, mistakes, selective memory, or institutional bias; a strong secondary source can explain those limitations and compare the item with a wider record.

For a fuller introduction, read Sources and Evidence: How Historians Evaluate the Past.

How facts are checked

Review focuses on the claims a reader needs in order to understand the event:

1. Confirm that the cited material concerns the same person, place, event, and date.
2. Separate the date of the event from later commemorations, announcements, ratifications, or publications.
3. Check names, titles, locations, chronology, and numerical claims against the source.
4. Determine whether multiple citations are independent or repeat one underlying account.
5. Compare conflicting accounts and identify the reason for disagreement where possible.
6. Write the summary at the level of certainty the surviving evidence supports.

Dates, calendars, and disputed details

Historical dates can differ because sources use different calendars, an event extended over several days, a decision and its public announcement occurred separately, or later traditions assigned a date that contemporary records do not confirm. When a precise anniversary is disputed, the entry should explain the issue, use qualified language, or remain unpublished until the evidence is adequate.

Quotations and translations

Quotations should be traceable to a source and should not be altered in a way that changes their meaning. Translations should identify the edition or institution when practical. Famous quotations that appear only in later retellings are not treated as contemporary evidence without qualification.

Links and access dates

Source records identify the title, publisher, URL, and date accessed when available. External pages can move, change, or disappear after publication. A broken link does not necessarily invalidate the underlying work, but it should be replaced or updated when a stable authoritative location can be found.

Corrections process

To report a possible error, provide the page URL, event headline, disputed wording, and supporting source material. Reports are evaluated against the available evidence and may result in a factual correction, clarified language, an additional citation, or no change when the issue is an interpretive disagreement rather than an error.

Send a correction or source suggestion.

Related policies

The Editorial Policy explains event selection, AI-assisted drafting, review, language, and updates. Last updated July 12, 2026.