How does bc years work

These abbreviations have a shorter history than BC and AD, although they still date from at least the early s. Since the Gregorian calendar has superseded other calendars to become the international standard, members of non-Christian groups may object to the explicitly Christian origins of BC and AD.

It is widely accepted that the actual birth of Jesus occurred at least two years before AD 1, and so some argue that explicitly linking years to an erroneous birthdate for Jesus is arbitrary or even misleading. In , education authorities in Australia were forced to deny that such a change had been planned for national school textbooks amid a similar controversy triggered by media reports. Passions are usually highest among those who see the adoption of a new system as an attempt to write Jesus Christ out of history.

They argue that the entire Gregorian Calendar is Christian in nature anyway, so why should we attempt to obscure that fact? Others ask why such a well-established and functional system should be replaced, arguing that the existence of two competing abbreviations is likely to cause confusion. Since there are compelling arguments for each system and both are in regular use, we do not recommend one over the other.

Given the choice, writers are free to apply their own preference or that of their audience, although they should use their chosen system consistently, meaning BC and CE should not be used together, or vice versa. There are also some typographical conventions to consider:. As a result, dates that occurred within the last few centuries are rarely marked with CE or AD. Dionysius never said how he determined the date of Jesus' birth, but some authors theorize that he used current beliefs about cosmology, planetary conjunctions and the precession of equinoxes to calculate the date.

Dionysius attempted to set A. The addition of the B. There was no year zero. However, zero did exist; our modern conception of zero was first published in A. The idea would not spread to medieval Christian Europe, however, until the 11th to 13th centuries. For example, if you need to work out how many years are between January 1, B.

However, you still have to adjust for the absence of year 0. You do this by removing 1 from your answer, so minus 1 is The calculation is a little more complicated when you are calculating partial years across B.

First, change the month of the year into decimal form. If 12 months is 1, then nine months is 0. Say you need to work out what calendar year was years before October A. The simplest method is to take the starting calendar year and figure out how much time has lapsed since January 1, A.

In other words, October in the year was 1, Then calculate This means 4, years before October A. Claire is a writer and editor with 18 years' experience.