public java.util.Date getStartTimestamp() {
        return this.startTimestamp;
    }
<p>
UTC timestamp at which the upgrade API call was made, in the format <code>yyyy-MM-ddTHH:mm:ssZ</code>.
</p>

@return UTC timestamp at which the upgrade API call was made, in the format <code>yyyy-MM-ddTHH:mm:ssZ</code>.
aws-java-sdk-opensearch/src/main/java/com/amazonaws/services/opensearch/model/UpgradeHistory.java