private void UpdateMaximum(PostedTime item)
 {
     if(Maximum == null || item.CompareTo(Maximum) > 0)
     {
         Maximum = item;
     }
 }
 private void UpdateMinimum(PostedTime item)
 {
     if(Minimum == null || item.CompareTo(Minimum) < 0)
     {
         Minimum = item;
     }
 }
 private void ReplaceCurrentMinimum(PostedTime replacement)
 {
     if(InnerItems.Count == 1 || replacement.CompareTo(Minimum) < 0)
     {
         Minimum = replacement;
     }
 }