public Builder setStartTime(com.google.protobuf.Duration.Builder builderForValue) {
      if (startTimeBuilder_ == null) {
        startTime_ = builderForValue.build();
      } else {
        startTimeBuilder_.setMessage(builderForValue.build());
      }
      bitField0_ |= 0x00000001;
      onChanged();
      return this;
    }
<pre>
Time offset relative to the beginning of the audio,
and corresponding to the start of the spoken word.
This field is only set if `enable_word_time_offsets=true` and only
in the top hypothesis.
This is an experimental feature and the accuracy of the time offset can
vary.
</pre>

<code>.google.protobuf.Duration start_time = 1;</code>
java-speech/proto-google-cloud-speech-v1/src/main/java/com/google/cloud/speech/v1/WordInfo.java