private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Timestamp,
            com.google.protobuf.Timestamp.Builder,
            com.google.protobuf.TimestampOrBuilder>
        getOldestEstimatedArrivalTimeFieldBuilder() {
      if (oldestEstimatedArrivalTimeBuilder_ == null) {
        oldestEstimatedArrivalTimeBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Timestamp,
                com.google.protobuf.Timestamp.Builder,
                com.google.protobuf.TimestampOrBuilder>(
                getOldestEstimatedArrivalTime(), getParentForChildren(), isClean());
        oldestEstimatedArrivalTime_ = null;
      }
      return oldestEstimatedArrivalTimeBuilder_;
    }
<pre>
Output only. An estimation of the nearest time in the future where a task
in the queue is scheduled to be executed.
</pre>

<code>
.google.protobuf.Timestamp oldest_estimated_arrival_time = 2 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-tasks/proto-google-cloud-tasks-v2beta3/src/main/java/com/google/cloud/tasks/v2beta3/QueueStats.java