The first century BC, sometimes known as the final century BC, began on January 1, 100 BC and concluded on January 31, 1 BC. The AD/BC notation does not include a year zero; nevertheless, astronomical year numbering includes a zero as well as a minus sign, thus "2 BC" equals "year-1." The first century AD (Anno Domini) begins.
In astronomy, a century is any period of exactly 100 years. The current era is called the 21st century because 2000 was an exact millennium year. Astronomers use the term centurie to refer to periods of 100 years or more. Thus, the Roman Republic lasted for about 200 years, and the Roman Empire lasted for almost 600 years. Modern estimates put the end date of the Roman Empire at around 400 AD, which is relatively recent in historical terms.
In mathematics and science, a century is a sequence of hundred values or units. In astronomy, physics, chemistry, biology and other sciences that use centuries as unit of time, a century begins with the year 0 and ends with 99 or 100. The year 0 marks the beginning of the epoch, also called a calendar cycle or time frame. By convention, the -th year of the epoch is designated Year 0 (or Year 1). Thus, the 20th century was declared by popular agreement to begin in 1901, rather than in 1900 as specified by the International Civil Service Commission that created the official calendar system for Britain.
In sociology, a century is a period of 100 years.
1 B.C. Because there is no year zero in this arrangement, AD 1 immediately succeeds BC 1. Dionysius Exiguus of Scythia Minor established this date method around 525, although it was not extensively utilized until the 9th century. The dating system used by Dionysius consisted of 18 months of 30 days each with 5 extra days at the end of every year.
The first year of AD was considered to begin on January 1, and during that year the number of days increased from 365 to 366. At the end of year one, December 31 was considered a new year's day, so year two began on January 1st and continued for another 365 days. This process would continue indefinitely if not interrupted by some other method of dating.
Year numbers were often abbreviated for convenience sake. So, for example, "AD 4" could be read as "Anno Domini 4".
Years before the birth of Christ were dated from A.D. 1 while years after his death were dated from B.C. 1. Thus, an event that took place in A.D. 100 would have been exactly 100 years after the death of Jesus Christ. Before the adoption of the Gregorian calendar in 1582, the era was divided into centuries based on the birth dates of Julius Caesar and Augustus, which made them both fall on August 25.
No, the BC (Before Christ) and AD (Anno Domini) systems were developed in AD 525 by a Roman Empire monk. There is no idea of zero in the Roman number system, which was still in use at the time. As a result, the day following December 31st, 1 BC, was January 1st, AD 1. By changing the starting point after each century, many generations could be counted from the same date.
The years were started at 0 because this is how dates were calculated in ancient Rome. The word "year" has only got its modern meaning in Europe - where our annual calendar is used - so dates were recorded by counting back from a single starting point. This point could be any time before or after the beginning of October, as it was then that the Romans adopted their new year. Since they had no month names to help them remember what happened in which month, they just made up new words for each month.
So, when did the years start? They started on January 1st, BC 772 or AD 1 if you prefer. Although most people today are more familiar with the BC/AD system, the older abbreviation B.C. (before Christ) is still used by some writers and scholars.
In Britain, January 1st was always New Year's Day until 1752 when it was moved to March 25th because February had 29 days instead of 28 like now. So, the years before 1752 were actually shorter than today!