Dates: BC dates [221]


Encoding of BC dates


The WWP encodes the value= of <date> for BC dates in the manner of the astronomers. Year 0 is the year preceding year 1 (a.k.a. 1 B.C.). Year -1 is the year preceding year 0 (a.k.a. 2 B.C.). Generally, year -n is the year which began n+1 years before the beginning of year 1 (so year -n = year n+1 B.C.). With the use of this astronomical system of year-numbering there are no limits to the dates which can be expressed in this date format, as long as we are consistent about using 4 digits for the year. Thus the Julian calendar was adopted in <date calendar="Gregorian" value="-0045">46 B.C.</date>. (From “The ISO Date Format” by Peter Meyer (

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