rem: PrintCellItem( Event *event, const QDate &day ) : mEvent( event ), mDay( day )
add: PrintCellItem( Event *event, const QDateTime &start, const QDateTime &end ) : mEvent( event ), mStart( start), mEnd( end )
context:     PrintCellItem( Event *event, const QDate &day )      : mEvent( event ), mDay( day )    {    }