@Override
 public void merge(MutableProfileFieldValueType into, ProfileFieldValueType from)
     throws MetricMergeException {
   DateHolder fromHolder = (DateHolder) from.getValueTypeMetrics(SIMPLE_NAME);
   if (fromHolder != null) {
     DateHolder dateHolder = getOrCreateDateHolder(into);
     dateHolder.offer(fromHolder.getMin());
     dateHolder.offer(fromHolder.getMax());
   }
 }
 public MutableProfileFieldValueTypeImpl(ProfileFieldValueType profileFieldValueType) {
   this(
       profileFieldValueType.getTypeName(),
       profileFieldValueType.getCount(),
       new HashMap<String, ValueTypeMetrics>(profileFieldValueType.getValueTypeMetricsMap()));
 }