The MEDIC ATNA API project provides a simple to use series of utility classes centered around creating IHE Audit Trail and Node Authentication (ATNA) audit messages (ITI-20)
The AuditMessage class has this constructor: AuditMessage(DateTime timeStamp, ActionType actionCode, OutcomeIndicator outcome, EventIdentifierType eventIdentifier, CodeValue<String> eventTypeCode)
However timeStamp is not used, and instead is assigned: EventDateTime = DateTime.Now,