BC ⇄ AD Year Difference Calculator
Compute the time between a BC/BCE year and an AD/CE year. Formula: D = BC + AD − 1 (no year zero).
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Year BC/BCE
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Switch label only (BC/BCE naming).
BC year must be ≥ 1.
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Year AD/CE
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Switch label only (AD/CE naming).
AD year must be ≥ 1.
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Time between
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Difference must be ≥ 0.
⚡Quick summary
Inputs
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Time between
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Also equals
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🧮Step-by-step derivation
Formula (no year zero):
D = BC + AD − 1Substitute:
D = …Solve:
…There is no year 0. 1 BC is followed immediately by AD 1.
📚Reference table & sources
| Item | Summary | Source |
|---|---|---|
| No year 0 | Timeline jumps from 1 BC to AD 1, so subtract 1 in the formula. | Wikipedia — Anno Domini |
| Formula | D = BC + AD − 1, where D is the number of full years between those years. |
Historical timeline convention |
| Labels | BC ≡ BCE; AD ≡ CE (naming only; values unchanged). | Style usage |