How we date

A range of years on its own tells a reader very little. The atlas names the level behind every range, so that a measured date is never confused with a typical one.

Measured

The monument itself was dated by measurement: a radiocarbon sample from its chamber or from the deposit it stood in, the ring of a timber, or an excavation that dated the layer beneath it. The range belongs to the sample, and the page links the report it came from.

Dated byRadiocarbon · excavation

Estimated

The date was inferred rather than measured. A written record places the monument in history, or the style of its carving is read against a dated sequence. An estimate is still a range, and the page says which kind of inference it is.

Dated byHistorical · stylistic · a stated source date

Typical for this type

Nobody has dated this monument. The range is the published range for its type in its region: what a Neolithic passage tomb in Scotland, or a Bronze Age mound in Denmark, is generally dated to. It is a real and sourced range. It was not measured here, and the page never pretends it was.

Dated byTypological estimate

Unknown

No source gives the site a date. The page says so rather than borrowing a range from somewhere else, and carries the facts that are known.

Dated byNo date in any source

Dating a monument means disturbing it. Excavation is expensive, slow and destructive, and radiocarbon needs an organic sample — charcoal from a burnt chamber, bone, a seed, a residue on a vessel. Almost nobody has paid for that at a field monument, so almost nobody has a measured date for one.

In the catalogue as it stands, 654 sites carries a date of its own. 98,432 sites carries the range published for its type in its region. That second number is not a failure of the record — a typological range is a real finding, and for most of the catalogue it is the best answer the published record gives.

The atlas keeps the two apart rather than blending them. A page that shows a typical range says so in the same line, so nobody has to guess which kind of number they are reading.

A prehistoric date is never given as one year. 3000 BCE implies a precision nobody has: it says the monument was raised in a year we can name, which no excavation has ever managed. Every date in the atlas is a range with a method and a note saying how the range was reached, and the earlier end of that range is the year the site began.

A range is not a hedge either. A range says what the evidence supports and nothing more: the span between the earliest and the latest year the sources give for the site itself. A wide range means the evidence is wide, and the page shows it wide.

BCE and CE

Before the common era and the common era. Inside the atlas the years before the common era are negative, so 3200 BCE is stored as -3200; the reader sees 3200 BCE. There is no year zero: 1 BCE is followed by 1 CE.

Beyond ten thousand years ago

A calendar year that far back is not a number a reader can hold in mind, and not one many sources agree on to the year. Beyond roughly 10,000 years ago the age is given as years ago instead — 12,500 years ago — so that the scale of the thing stays clear.

Circa

A range that is an estimate is marked c. before it, the way a book marks an approximate date. The c. is not decoration: it is the difference between a measured year and an inferred one.

A monument can carry several sourced claims about its age, and they can contradict each other. The atlas shows the mainstream range first, then keeps the alternative claims in their own block, each with the source that makes it and how that claim stands — whether it was tested and did not hold, whether it is still debated, or whether nobody has tested it at all.

The atlas never merges them into a single number, and it never strikes a claim out. A claim that has been tested and did not hold is still shown, in its own row, with the verdict the source gives.

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