I can confirm this bug.
KMail 1.13.5, KDE 4.5.2

I can confirm this bug.
KMail 1.13.5, KDE 4.4.5

The problem is that the list widget uses a lexicographical comparison by default. To solve this issue, instead of using QTreeWidgetItem objects to represent search results, a new class has to derived here which re-implements the sorting function (more specifically, how two entries are compared).

My idea would be as follows (not compiled, not tested, may not work at all!):



const int ColumnDate=2;

class MatchListViewItem : public QTreeWidgetItem
{
	private:
		MatchListView *parent;
		
	public:
		
MatchListViewItem(MatchListView *p)
: QTreeWidgetItem(p), parent(p)
{
	// empty
};

bool operator<( const QTreeWidgetItem & other ) const
{
	switch(parent->sortColumn()) {
		case ColumnDate:
			return QDate::fromString(text(ColumnDate)).operator<(QDate::fromString(other.text(ColumnDate)));
		default:
	return QTreeWidgetItem::operator<(other);
	}
}
};


In function SearchWindow::slotAddMsg, use this class instead of QTreeWidgetItem when adding more results.
Maybe I'll test and refine this code later today...

(In reply to comment #3)
> The problem is that the list widget uses a lexicographical comparison by
> default. To solve this issue, instead of using QTreeWidgetItem objects to
> represent search results, a new class has to derived here which re-implements
> the sorting function (more specifically, how two entries are compared).
> [...]
> In function SearchWindow::slotAddMsg, use this class instead of QTreeWidgetItem
> when adding more results.
> Maybe I'll test and refine this code later today...

My simple code above would not work, as the date strings are localized and not easy to compare. A better implementation would be to use nice model/view approach which has already been implemented in trunk and 4.5beta1 (not tested myself, yet).

Therefore I propose to close this bug as soon as Kontact / KMail 4.5 becomes stable. Maybe mark this bug until then as WONTFIX?

I fixed this bug yesterday
I close it