Astronomical dating is highly accurate. The "astronomical" dating system refers to an alternative method of numbering years. It includes the year "0" and eliminates the need for any prefixes or suffixes by attributing the arithmetic sign to the date. Thus, the astronomical date for AD 2000 is simply +2000 or 2000. The astronomical year 0 corresponds to the year 1 BC, while the astronomical year -1 corresponds to 2 BC. In general, any given year "n BC" becomes "-(n-1)" in the astronomical year numbering system. Historians should take care to note the numerical difference of one year between "BC" dates and astronomical dates.
Astronomical date numbering was developed for astronomical calculations 
The chronology placing the date for the destruction of Jerusalem in 587 BC is derived from records which have come down to us in the form of clay tablets, the majority of which are documents made during the Seleucid period (4th century BC). Many of these documents make reference to astronomical events, such as eclipses of the sun and moon, which are numbered to the years of various kings; however, the accuracy of the year numbers (and in some cases the king so named) in these documents is of a questionable nature.