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

@param startTimestamp
       UTC timestamp at which the upgrade API call was made, in the format <code>yyyy-MM-ddTHH:mm:ssZ</code>.
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-opensearch/src/main/java/com/amazonaws/services/opensearch/model/UpgradeHistory.java