Astronomical year numbering in the context of "1st century BC"

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⭐ Core Definition: Astronomical year numbering

Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly. Thus, it has a year 0; the years before that are designated with negative numbers and the years after that are designated with positive numbers. Astronomers use the Julian calendar for years before 1582, including the year 0, and the Gregorian calendar for years after 1582, as exemplified by Jacques Cassini (1740), Simon Newcomb (1898) and Fred Espenak (2007).

The prefix AD and the suffixes CE, BC or BCE (Common Era, Before Christ or Before Common Era) are dropped. The year 1 BC/BCE is numbered 0, the year 2 BC is numbered −1, and in general the year n BC/BCE is numbered "−(n − 1)" (a negative number equal to 1 − n). The numbers of AD/CE years are not changed and are written with either no sign or a positive sign; thus in general n AD/CE is simply n or +n. For normal calculation a number zero is often needed, here most notably when calculating the number of years in a period that spans the epoch; the end years need only be subtracted from each other.

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👉 Astronomical year numbering in the context of 1st century BC

The 1st century BC, also known as the last century BC and the last century BCE, started on the first day of 100 BC and ended on the last day of 1 BC. The AD/BC notation does not use a year zero; however, astronomical year numbering does use a zero, as well as a minus sign, so "2 BC" is equal to "year –1". 1st century AD (Anno Domini) follows.

In the course of the century, all the remaining independent lands surrounding the Mediterranean Sea were steadily brought under Roman control, being ruled either directly under governors or through puppet kings appointed by Rome. The Roman state itself was plunged into civil war several times, finally resulting in the marginalization of its 500-year-old Roman Republic, and the embodiment of total state power in a single man—the Roman emperor.

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Astronomical year numbering in the context of Year zero

A year zero does not exist in the Anno Domini (AD) calendar year system commonly used to number years in the Gregorian calendar (or in its predecessor, the Julian calendar); in this system, the year 1 BC is followed directly by year AD 1 (which is the year of the epoch of the era). However, there is a year zero in both the astronomical year numbering system (where it coincides with the Julian year 1 BC), and the ISO 8601:2004 system, a data interchange standard for certain time and calendar information (where year zero coincides with the Gregorian year 1 BC; see: Holocene calendar § Conversion). There is also a year zero in most Buddhist and Hindu calendars.

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LINKED FROM (PARENTS)
← 1st century BC ← 1st century BCE ← Year zero
LINKS TO (CHILDREN)
Anno Domini → Common Era → Decimal → Integer → 0 (year) → Negative number → Julian calendar → Gregorian calendar → Jacques Cassini → Simon Newcomb → Fred Espenak → 0 (number) → Epoch (astronomy) →