public void setAlertTimestamp(Long alertTimestamp) {
    this.alertTimestamp = alertTimestamp;
  }
Sets the time that the alert instace was received. This should be the
value, in milliseconds, since the UNIX/Java epoch, represented in UTC time.

@param alertTimestamp
         the time of the alert instance (not {@code null}).
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertHistoryEntity.java