In dateValue and other places ABNF allows year zero (or negative).

Now with OData V4 there is no specific reference to XML Schema Part 2 DataTypes (Second Edition) although OData 3 spec did have a reference to that document for dateTimeOffsetLiteral, so perhaps there is an unwritten understanding that OData lexical representations match those defined in XML Schema Part 2 Datatypes (Second Edition).

In any case, see https://www.w3.org/TR/xmlschema-2/#year-zero

Key questions: (see the linked XML Schema section)

(1) Is year 0 valid in OData Date/DateTimeXXX values (including Edm.String with Core.DateTime annotation in 4.01)? If so, what does it mean? (e.g. 1 BCE)

(2) What is the interpretation of negative years in OData Date/DateTimeXXX values? Is year -1 equivalent to 1 BCE, or to 2 BCE?