# Astronomical year count

The **astronomical era** is a common especially among astronomers year count for the year prior to the year 1 n. Chr. While in the usual counting of the years " before Christ " and " BC " the year that the year 1 Chr. . precedes when year 1 BC Is counted, this year is referred to as year 0 in the astronomical year counting . The years before that are denoted by negative whole numbers , the additions “n. Chr. "And" v. Chr. ”Are not used. The year 1 BC So the year 0 becomes the year 2 BC. To the year −1, the year 3 BC BC to the year −2 etc.

As usual, the astronomical year counting uses the Gregorian calendar for years after the Gregorian calendar reform in 1582 , and the Julian calendar for the years before that . The switching control of the Julian calendar that all year, the year with 4 divisible is, leap years are valid with the astronomical year counting for the year 0 and the year with a negative year. For example, the years 0 (1 B.C.), −4 (5 B.C.), −8 (9 B.C.), and −12 (13 B.C.) are leap years. When counting "BC" these are the years, their year at Division by four the rest follows. 1