How we source
How History Timelines researches, sources, and reviews every timeline on the site.
Every date and fact on History Timelines is checked against a named, publicly available source: encyclopedic references, official archives, and established biographical or historical records. Each timeline page lists its sources and the date it was last reviewed.
What Counts as a Source Here
We draw on general encyclopedic references, national archives and libraries, official government and institutional records (presidential libraries, national park services, state historical societies), and recognized biographical and historical reference works. Where a fact is genuinely contested among historians (a disputed date, an unclear cause, a debated motive), we say so in the text rather than picking a single account and presenting it as settled.
How a Timeline Gets Built
Each page starts from the same structure: a dated sequence of milestone events, followed by narrative sections that explain how those events connect: causes, consequences, and context that a bare date list can't carry on its own. Names, dates, and figures are checked against at least one named reference before publication, and we avoid restating a single secondary source's specific numbers as if they were independently verified when they aren't.
Corrections and Updates
History doesn't change, but the record of it does: new scholarship, newly opened archives, and, for people who are still living, ongoing events all mean a page can go out of date. Each timeline shows a last-updated date, and pages are revisited periodically rather than treated as permanently finished. If you spot an error, the contact page has a way to reach us, and confirmed corrections are made directly to the page.
This applies especially to timelines covering people, organizations, or situations that are still active. A biography of someone still working, or a country's timeline while its politics are still unfolding, is checked more often than a page covering an event that ended a century ago; the goal is for a "last updated" date to mean something, not just to exist.
What We Don't Do
We don't invent quotes, statistics, or specific figures that aren't in a checkable source. We don't present a single interpretation of a contested historical question as the only one. And we don't treat a Wikipedia mirror or an unsourced blog post as equivalent to a primary archive, an established encyclopedic reference, or an official institutional record.
Why Sourcing Matters More for a Timeline than for Prose
A timeline compresses a life or an event into a short sequence of dated points, and that compression is exactly where errors slip in unnoticed: a date rounded for convenience, a cause simplified past the point of accuracy, a minor figure's role overstated because it makes a cleaner story. Treating each entry as a claim that needs a source, rather than as a fact everyone already knows, is the discipline that keeps a timeline trustworthy rather than merely tidy.
Frequently Asked Questions
Are the sources on each page real, checkable references?
Yes. Every timeline page lists the named references used to check its facts, so a reader can verify anything on the page independently.
How often are timelines reviewed for accuracy?
Pages are reviewed on an ongoing schedule, with the last-reviewed date shown on each page. Timelines covering people or topics still in the news are checked more frequently.
What happens if a factual error is found?
Confirmed errors are corrected directly on the page, and the last-updated date is refreshed to reflect the change.
Do you cite primary sources or secondary references?
Both, depending on availability: official archives and institutional records where they exist, and established encyclopedic or biographical references elsewhere.