public Long getAlertTimestamp() {
    return alertTimestamp;
  }
Gets the time that the alert instace was received. This will be the value,
in milliseconds, since the UNIX/Java epoch, represented in UTC time.

@return the time of the alert instance (never {@code null}).
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertHistoryEntity.java