Keep the calibration label
Oxford’s Radiocarbon Accelerator Unit explains that radiocarbon measurements are commonly expressed as notional years before 1950. Because atmospheric radiocarbon has varied, calibration compares measurements with material of known age to estimate possible calendar dates. The prefixes and uncertainty information are essential parts of the result.
Do not subtract an uncalibrated BP number from the current year to create a historical date. That combines the wrong reference point with an unperformed calibration.
Read the range rather than inventing one year
Oxford’s result explanation shows that calibration can produce several possible calendar ranges with stated probabilities. A documentary may round this to an accessible period, but the laboratory result contains more detail. Preserve a range and its qualification when exact chronology matters.
Do not average separated ranges into a date the source did not report. Likewise, a plus-or-minus value attached to a conventional measurement should not automatically be copied as the same calendar-year uncertainty after calibration.
Identify what was sampled
The Unit’s dating explanation distinguishes organic materials from objects such as stone, metal or pottery that usually cannot be directly dated by this method without relevant organic material. A date from charcoal associated with an object is not simply a direct measurement of the object’s manufacture.
Record the sampled material and the relationship claimed between the sample and the event. The age of a sample, the use of an object and the deposition of a site layer can be different chronological questions.
Trace the programme’s claim
Save the episode, site, sample description, laboratory reference if supplied and the date exactly as reported, including cal, BP, BCE or CE and uncertainty. Consult the excavation or laboratory explanation before translating a technical result into a precise historical statement.
This article explains notation, not how to run a dating analysis. If the programme supplies only an approximate date, retain that level of precision. A useful viewing note says what material was dated and how the result supports the story, leaving any uncertain association visible rather than turning a scientific estimate into an unsupported exact anniversary.
Related questions
Does BP mean years before the day I watch?
In conventional radiocarbon reporting, its reference is 1950.
Can I directly subtract an uncalibrated age to get BCE?
No. Calibration and the reported uncertainty matter.
Sources and scope
Scope notes distinguish published documentation, supplied information and editorial methods. They do not report a hands-on service test.
- Oxford ORAU: radiocarbon results — Current primary explanation of notional BP ages, calibration and ranges.
- Oxford ORAU: calibration — Explains 1950 reference and calibrated notation.
- Oxford ORAU: dating materials — Explains suitable materials and limits on direct dating.
