BC to AD Calendar Converter
Convert dates between BC/AD and BCE/CE calendar systems.
Calculate the number of years between two dates across the BC/AD boundary.
BC/AD vs BCE/CE BC (Before Christ) and AD (Anno Domini, Latin for “in the year of our Lord”) are the traditional Western calendar designations. BCE (Before Common Era) and CE (Common Era) are the modern secular equivalents. The numbering is identical: 500 BC = 500 BCE, and AD 2024 = 2024 CE.
There Is No Year Zero In the BC/AD system, there is no year 0. The calendar goes directly from 1 BC to AD 1. This means the number of years between dates that cross the BC/AD boundary is one less than you might expect. For example, from 3 BC to AD 3 is only 5 years (not 6), because there is no year 0.
Calculating Years Between BC and AD Dates Years apart = (BC year) + (AD year) - 1. For example, from 44 BC (Julius Caesar’s assassination) to AD 2024: 44 + 2024 - 1 = 2,067 years.
Astronomical Year Numbering Astronomers use a different convention that includes year 0: 1 BC = year 0, 2 BC = year -1, 3 BC = year -2, etc. This simplifies arithmetic: the interval between any two years is simply the difference of their year numbers.
Historical Context The AD system was devised by Dionysius Exiguus in AD 525 in Rome. He was trying to calculate the correct date for Easter. The BC/AD system did not become widely used in Europe until the 8th century, when the English monk Bede popularized it in his historical works.