Before Present (BP) is a year numbering system, used for the far past times, relating dates to the year 1950. For example, 12,000 BP means 12,000 years before 1950. This is a commonly-used year numbering system in carbon-14 dating.

Why 1950?

Scientists established 1950 as the benchmark date for the BP system because it is the year in which calibration curves for carbon-14 dating were established. 1950 also predates atmospheric testing of nuclear weapons.

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