[Property] time-stamp [Type] xs:integer? [Value] 
The time (in milliseconds relative to the epoch) at which the event was created. Due to the fact that some systems may not provide this information the value of timeStamp may be not available for all events. When not available, an empty sequence will be returned. Examples of epoch time are the time of the system start or 0:0:0 UTC 1st January 1970.