How the timelines are made
Who compiles these timelines
Michael Yan compiles these timelines. He makes Chronarium as a solo developer, and the company behind it is Polymath Studios LLC.
He set the rules for research and checking, and he signed off the page template and the three sample pages. He reads every correction that comes in.
Michael Yan is not a historian, and no historian has reviewed any of these pages.
How entries are chosen
A timeline holds 60 to 121 entries. An entry can be an event, a period, a person, a place, an organisation or a work. Entries are picked to cover every lane, meaning each region or theme, across the full stretch of the period rather than only its famous moments.
Each entry gets an importance rank on a scale that starts at 1 (anchor) and ends at 4 (detail). The picture displays ranks 1 and 2 only; this is Chronarium's Major only view. The table lists them all, and where coverage of a period is thin the page is marked 'selective coverage'.
A few entries begin before the span the page covers or end after it. They are there as background, and the facts strip adds them to its tally. Inside each period, the rows appear in order of start date.
Sources and checks
Every date on these timelines rests on two published sources, each on a different website, and each source states the date itself. Wikipedia may appear as one of them, never as both.
Each source's date wording is saved as written, and a script confirms that this wording appears on the source's page. Some sites do not allow script access, Britannica among them; for those, the wording was checked in a browser instead. A separate step confirms the date with a third source, hosted on a site different from the first two. About one date in seven received an extra spot check against further pages, carried out by an AI model.
Before anything enters the project file, Chronarium's own date reader reads each date, and the timeline picture shown on the page is exported by Chronarium from that same file. Every page closes with its sources, naming the publisher and giving a link for each.
Where AI is used
Every date is verified against two published sources, and automated (AI) help does much of the groundwork: it finds the sources, drafts the notes, and runs the third-source check, but it is software, not a historian. Scripts scan every note for copied wording and for numbers that appear nowhere in its facts, and a second model checks the notes as well. The rules are set by Michael Yan, who also reviews how the method works, how the pages are laid out, and a sample of the results; no historian has reviewed the pages.
What the date marks mean
A 'c.' mark means the date is approximate: the sources say around or about, or their dates differ by no more than that mark allows. On a historical date, sources 1 to 3 years apart fall under one 'c.', and a wider gap is marked '?' instead. For very old dates the allowance grows with age: about 10% for dates older than 100,000 years ago, around 7 to 8% from there to 10,000 BCE, and roughly 3% of the date's age after that.
A '?' means the sources conflict on that date, on whichever end of the entry it appears. A 'Sources differ' line beneath the note lists what each source gives.
'Scope' means sources attach dates to different definitions of the same thing, and the line states which definition the entry follows. The Holocaust is one case: 1933 to 1945 when it covers the persecution and murder of Europe's Jews, 1941 to 1945 when it covers the systematic mass murder. A span can also carry a mark on just one end, such as a settled death date next to a birth year that remains disputed.
Calendar conventions
Years are written as BCE and CE. No year zero exists, so 1 BCE passes straight into 1 CE.
Anything more than 100,000 years old is given as years ago, not as a calendar year.
Dates from Europe before 1582 use the Julian calendar, the way reference works record them. Mesopotamian dates use the middle chronology, which the Ancient Mesopotamia page notes.
Page dates and corrections
'Published' is the date the page first appeared. 'Updated' moves only when the content itself changes: a date, a mark, a claim in a note, what the page covers or which sources it cites. A rebuild on its own never moves it.
Errors can be reported to support@chronarium.app; say which page and which entry. Each row carries a # link that identifies it, so include that link to pinpoint the exact line.
Every correction is verified against the sources before anything on the page changes. Only then does the 'Updated' date move.