Era
A linear (non-cyclic) frame of reference used to assign numbers to years. This class can be used for any year numbering system, even if the definition of "year" in that system doesn't match the one of the Gregorian calendar. For instance Roman reigns (like they reign of Claudius) or Japanese eras (like the Reiwa era) can be encoded as instances of time:Era. This specification makes no assumption about the possibility of a year 0, or of years with negative indexes. An era can correspond to a temporal entity (ex: a Roman Emperor reign) but does not have to (ex: the Common Era, which doesn't have an upper limit).
in era
Era indication
ex:TwentyTwenty a time:GeneralDateTimeDescription ; time:year "0002"^^time:generalYear ; time:era ex:Reiwa ; .
in reign of
The object of this property is the person whose reign is associated with the era. In some cases multiple eras are associated with the same reign (especially in the late Chinese context). No range is indicated so that the associated person can have any relevant type.
ex:ClaudiusRegnalYears a time:Era ; time:reignOf ex:Claudius ; .
Common Era
The Era of the modern gregorian calendar, so that a time:generalYear associated with this era is roughly equivalent to a xs:gYear. The general year associated with this era can be a non-gregorian year. For example, some Chinese calendars may indicate years in the Common Era, even though the Chinese year starts and ends after the gregorian one.
An extension of the OWL-Time ontology - Eras