timestamp

@XmlSerialName(value = "when")

@XmlElement

Specifies a single moment in time. The value is a dateTime, which can be one of the following:

dateTime (YYYY-MM-DDThh:mm:ssZ) or (YYYY-MM-DDThh:mm:sszzzzzz) gives second resolution
date (YYYY-MM-DD) gives day resolution
gYearMonth (YYYY-MM) gives month resolution
gYear (YYYY) gives year resolution