@Override
  public String getDisplayString(String[] children) {
    assert (children.length == 1);
    StringBuilder sb = new StringBuilder();
    sb.append("CAST( ");
    sb.append(children[0]);
    sb.append(" AS ");
    sb.append(typeInfo.getTypeName());
    sb.append(")");
    return sb.toString();
  }
Convert from string to TIMESTAMP WITH LOCAL TIME ZONE.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFToTimestampLocalTZ.java