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BC to AD Years Calculator: Years Between Dates Across BC and AD (No Year Zero)

Count the years between any BC and AD years, or add and subtract years across the BC/AD line, with no year zero, plus astronomical, Holocene, AUC and BP years.

Calculate

Start year

Start year era

End year

End year era

Operation

Number of years

Show eras as

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How it works

Astronomical year: n BC → 1 − n, AD n → n · Years between = astronomical end year − astronomical start year · Across the line: years = BC year + AD year − 1 · Both BC: years = earlier BC year − later BC year · Add years: result = astronomical year + years, then 0 → 1 BC, −1 → 2 BC… · Holocene year = astronomical + 10,000 · AUC = astronomical + 753 · BP = 1950 − astronomical

The BC/AD (or BCE/CE) system has no year zero: the year before AD 1 is 1 BC. That is why you cannot simply add the two year numbers when you count across the line. From 500 BC to AD 500 is 999 years, not 1,000. The calculator converts each year to astronomical numbering, where 1 BC is 0, 2 BC is −1 and n BC is 1 − n, and then subtracts. The same conversion works for adding or subtracting years, for example 1,000 years after 44 BC is AD 957. You also get the inclusive count (both the first and last years counted, as in a reign "from 1 BC to AD 1" of two calendar years), centuries, the ISO 8601 year used by computers (where 0000 is 1 BC), and the year in other common systems: the Holocene era (HE, which adds 10,000 to avoid negative years), Ab urbe condita (AUC, years from the founding of Rome in 753 BC) and Before Present (BP, years before 1950, used in radiocarbon dating). Years ago are counted from the current year. The date add/subtract and years-between calculators on this site work with full dates from AD 1 onward. This one counts whole years and handles the missing year zero when a span crosses from BC into AD.

Worked example

Julius Caesar was killed in 44 BC. To count the years to AD 2026, convert 44 BC to the astronomical year 1 − 44 = −43. Then 2026 − (−43) = 2,069 years, the same as the shortcut 44 + 2026 − 1 = 2,069. Counting both 44 BC and AD 2026 gives 2,070 years. In other systems 44 BC is the 1st century BC, 9,957 HE, 710 AUC and 1,993 BP.

Sources: Wikipedia: Year zero (no year 0, astronomical numbering, 500 BC to AD 500 = 999 years) · Omni Calculator: BC to AD (BC + AD − 1, 1400 BC to AD 2022 example) · calculate.co.nz: BC to AD calculator (44 BC to AD 2026 = 2,069 years)

Frequently asked questions

How do you calculate years from BC to AD?

Add the BC year and the AD year and subtract 1, because there is no year 0. From 1400 BC to AD 2022 is 1,400 + 2,022 − 1 = 3,421 years. If both years are BC, subtract the smaller number from the larger.

Is there a year 0?

Not in the BC/AD calendar used by historians: 1 BC is followed directly by AD 1. Astronomers and the ISO 8601 standard do use a year 0, which equals 1 BC, so that year arithmetic works with ordinary subtraction.

How many years ago was 500 BC?

From 500 BC to AD 2026 is 500 + 2,026 − 1 = 2,525 years. In general, a BC year was (BC year + current year − 1) years ago.

What is the difference between BC/AD and BCE/CE?

Only the labels. BCE (Before Common Era) uses the same numbers as BC, and CE (Common Era) the same as AD. 44 BC is 44 BCE and AD 2026 is 2026 CE. AD goes before the number by tradition; CE, BC and BCE go after it.

Which century is 44 BC?

The 1st century BC, which runs from 100 BC to 1 BC. Centuries BC count backwards, so the 5th century BC is 500 BC to 401 BC.

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This calculator is for educational purposes. Double-check important results before acting on them.