protected void evaluate(LongColumnVector outputColVector, BytesColumnVector inV, int i) {
    String dateString = new String(inV.vector[i], inV.start[i], inV.length[i], StandardCharsets.UTF_8);
    Date hDate = DateParser.parseDate(dateString);
    if (hDate != null) {
      outputColVector.vector[i] = DateWritableV2.dateToDays(hDate);
      return;
    }
    setNull(outputColVector, i);
  }
Casts a string vector to a date vector.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/CastStringToDate.java