# 0 (year)

A year zero does not exist in the applied by historians traditional Christian era, but in the modern annual count of astronomers.

In the traditional system the years with ordinal numbers are counted before and after the birth of Christ: The year 1 BC, 31 December (1 BC), the next day, January 1, the year begins 1 AD birth (1 AD).

Astronomical year count however uses the extended to the zero and negative numbers, natural numbers, integers, the so-called. The contained in this number sequence 0 is year 1 BC, the number -1 to the year 2 BC assigned.

## Comparison of traditional and astronomical years counting

In the traditional system, the years from " Birth of Christ" each beginning with 1 even in the past and counted once in the future. The system consists of two independent chronologies based on the natural numbers.

The system of astronomers is a continuous chronology on the basis of whole numbers that matches the natural numbers with the traditional system.

In contrast to past years, counting the astronomical count carries a uniform calendar math. All formulas and relations that can be prepared the same for all years of the world on the basis of astronomical years counting, break apart into two heterogeneous parts in the historical year count.

The year 2 BC, 1 BC, 1 AD (or 2 AC, 1 AC, 1 AD) the historical annual census in hot astronomical counting -1, 0, 1

Younger Astronomy manuals explain the differences as follows:

" When a new year count is started, you have to clarify how the preceding year shall be designated. Venerable Bede, English historian of the eighth century, founded a practice, such as the A. D. 1 year ahead of the years are to be counted. [ ... ] This is the year A. D. 1 year 1 BC ahead without a Year 0 in between. Because of its numerical discontinuity of this, historical ' system for the difference between ancient and modern data is cumbersome. Astronomers use today 1 for A. D. 1 And the year A. D. 1 is the year 0, the year that preceded -1. Since the use of zero evolved slowly in Europe, this astronomical ' system late. It was introduced in the 18th century by Jacques Cassini. "

"Between astronomers and historians, there is difference of opinion, are such as to count the years before the year 1. In this book, the years counted before Christ 'on astronomical way. The year before year 1 is thus the year zero, and the year that was before this year, the year -1. The year, which historians describe as 585 BC, is actually the year -584. ( For negative year numbers is ' not used!, -584 BC ' before Christ, for example, is wrong. ) Astronomical way to include the negative years, is the only one which is suitable for arithmetic purposes. For example, the rule for divisibility by 4 is no longer valid for determining the Julian leap years in the past counting; these years are actually 1, 5, 9, 13, ... BC. In the astronomical number, however, these leap years than 0, -4, -8, -12, designated [ ... ] and the rule of divisibility by four remain. "

## Reasons for the absence of the year zero in the traditional Christian era

With the establishment of the Christian era, you would have no year zero can name, because the zero was not yet in use. But your not possible use was not the decisive reason for their absence in the traditional yearly counting. It is basically in the logic of the Count ends, so also today, only existing things - both real and abstract - to capture.

A report of a football game could be for example: " The remaining snow could be removed only at the last minute before kick-off the playing field. [ ... ] Already in the first minute after the whistle was a goal. " The minute before the game would never be understood as zero minutes. In this example, however, the problem arises that one to kick yourself (or figuratively Nativity) time can not define: The kick-off was therefore " between the minutes before kick-off " and " the minute after the kick-off " instead of ( or Jesus was born between the year 1 " before his birth " and the year 1 " after his birth ").

At that time the absence of zero is indicated by the then used Roman numerals, they do not have a symbol for it. In the time -driven, developed in ancient Greece geometrical mathematics, the zero is not needed. The Indian-born concept of zero was first noted at about the turn of the millennium of Gerbert of Aurillac in the Christian world, introduced in 1202 by Leonardo Fibonacci ( Liber abaci ) and applied since the Renaissance. A visible sign of the calculation with the zero was the use of the acquired by the Arabs digit zero.

In the Christian era is compared to regnal years counted ancient time calculations (for example, after Diocletian ) only exchanged a rule beginning with the birth of a religious founder.

## History of astronomical years counting

The annual scientific count is commonly referred to as astronomical years counting, because it is particularly used by astronomers preferred. The thing has nothing to do with astronomy at its core, but with calendar math. One can also speak of the mathematical counting.

Most likely originates with the idea to replace the traditional annual census by scientific yearly counting, in which the year is called before the year 1 with the number 0, of the Italian astrologer Luca Gaurico ( 1476-1558 ). Gaurico justified its reduction arithmetic. As an astrologer, he was interested in reflections in the chronology, he needed the year zero as the center of symmetry. In the 17th century astronomical years counting on the Academy of Sciences at Paris, was common, as is apparent from the presentation of the astronomer Giovanni Domenico Cassini in 1696. Publik the new counting method then was mainly through his son Jacques Cassini, who used it in astronomical tables. Often you hold today Jacques Cassini for the father of astronomical years counting.

## Comparison between modern and Roman era

The traditional historical era is equivalent to the Roman Calendar of the Christian era, but used despite missing year zero the Arabic number system. The astronomical chronology has this year zero. The year 1 BC corresponds to the year 753 after the foundation of Rome, according to legend.

Comments on the table

## Criticism of the standard ISO 8601

A controversial definition created by the International Organization for Standardization standard ISO with their 8,601th Therein the Gregorian calendar, a Leap year is allocated, and it is declared a proleptic calendar, which ranks well in the past.

- The Gregorian calendar was introduced in 1582 and not proleptically understood by the Reformers in contrast to the Julian Calendar as expressly ( not even before the time of the reform).
- For astronomers, the Gregorian 400 -year cycle is unfavorable, within which the centuries have unequal lengths. Astronomical calculations need a uniform time, which is why astronomers today first and always expect in Julian centuries and correct all data after 4 October 1582 Gregorian date until the end of the calculations. They are therefore the ISO 8601:1988 standard EN 28601:1992 = continue hardly apply.
- Historians have never used the year zero. You use for the past the familiar, proleptic, Julian calendar of the Christian era, so no year zero. Thus, it is not to be expected that the historian ISO standard 8601 per implement. A redating of all historical events, according to which ( in ISO notation: -0043-03-13 ) on 15 March 44 BC now on March 13th of the year -43 about Julius Caesar was murdered instead, is not to be expected.
- In computer date formats are converted always in relation to a younger time. Today it is mostly January 1, 1970, 12:00 UT (see Unix time). Therefore, the computer science has no need for a proleptic Gregorian calendar with a year of zero.