How to use XSD:dateTime for BCE dates?

[stephenhart8]

The most commonly used standard in managing dates is XSD:dateTime. It indicates the year, month, day, hours, minutes and seconds of an event. For instance, "2002-10-09T19:00:00" amounts to the 9th of October 2002, at 7pm (time zones have been omitted in CHIN’s use of the standard, for simplicity of use, and also because the timezone is often not known).

However, things are complicated when documenting events that happened before the year 1 CE, or in other words, dates before the common era (BCE).

Depending of the version of XSD:dateTime, there are two ways of documenting those "negative" dates:

• [Version 1.0](https://www.w3.org/TR/xmlschema-2/#dateTime](https://www.w3.org/TR/xmlschema-2/#dateTime): In this version, the value 0001 is interpreted as being year 1 CE, and -0001 as being year 1 BCE. As there is no year 0, the value 0000 is considered as an invalid lexical representation (Biron & Malhotra 2004);
• [Version 1.1](https://www.w3.org/TR/xmlschema11-2/#dateTime](https://www.w3.org/TR/xmlschema11-2/#dateTime): In this more recent version, the value 0000 is accepted and valid, and represents the year 1 BCE. The value -0001 thus represents year 2 BCE. This representation is said to simplify the interval arithmetic, but can obviously create some difficulties in the recording and mapping of dates before the common era.

Both options seem problematic, either from a computational standpoint (problems calculating intervals) or from a display standpoint (a shift of one year between the year recorded and the number encoded).

• Would there be other standards that could solve those issues?
• If not, and we decide to stick to XSD:dateTime, which version should be used? (It seems for me that the version 1.1 creates more problems than it solves)