2.2.2 [W3C-XSD] Section 3.2.11, gYear
Since the lexical representation allows an optional time zone indicator, gYear values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gYear values are considered as periods of time, the order relation on gYear values is the order relation on their starting instants. This is discussed in Order relation on dateTime (§184.108.40.206). See also Adding durations to dateTimes (§E). Pairs of gYear values with or without time zone indicators are totally ordered.
Indeterminate comparisons, such
2010, are considered to be determinate.