public Builder clearStart() {
      bitField0_ = (bitField0_ & ~0x00000001);
      start_ = null;
      if (startBuilder_ != null) {
        startBuilder_.dispose();
        startBuilder_ = null;
      }
      onChanged();
      return this;
    }
<pre>
Start date time.
</pre>

<code>.google.type.DateTime start = 1;</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/DateTimeRange.java