@Override
      protected void updateMin(Object minValue, DateObjectInspector minFieldOI) {
        if ((minValue != null) && (min == null ||
            min.compareTo(minFieldOI.getPrimitiveWritableObject(minValue)) > 0)) {
          // DateWritableV2 is mutable, DateStatsAgg needs its own copy
          min = new DateWritableV2(minFieldOI.getPrimitiveWritableObject(minValue));
        }
      }
GenericUDAFDateStatsEvaluator
High/low value will be saved in stats DB as long value representing days since epoch.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDAFComputeStats.java