I'm trying to send customers a receipt via email. I'd like each item in their receipt to be sorted by date (starting with the most recent purchase). 

I'm using AMPScript to populate the emails by invoking the LookupOrderedRows() function to grab rows from a Data Extension, where each row represents an item purchased. Unfortunately, simply specifying something like 'Date Desc' in LookupOrderedRows()  is insufficient, since this just sorts by characters.

Is there a way I can sort these rows by date? I'm fine with workarounds.

Here's my code:

        <table>
          <tr>
            <th>
              Reciept Number
            </th>
            <th>
             Purchase Date
            </th>
            <th>
             Membership Package
            </th>
            <th>
             Total Membership Price
            </th>
          </tr>
    %%[
        var @CustomerID, @rows, @row, @rowCount, @i, @ReceiptNumber, @PurchaseDate, @Package, @Price
        set @CustomerID = _SubscriberKey
        set @rows = LookupOrderedRows('DE1', '0','Date DESC','ID', @CustomerID)
        set @rowCount = rowcount(@rows)
        if @rowCount > 0 then
         for @i = 1 to @rowCount do 
          set @row = row(@rows,@i)
          set @ReceiptNumber = field(@row,'Receipt Number') 
          set @PurchaseDate = field(@row,'Date')
          set @Package = field(@row,'Item') 
          set @Price = field(@row,'Price')
        ]%%
         <tr>
          <td>
            %%=v(@ReceiptNumber)=%%
          </td>
          <td>
            %%=v(@PurchaseDate)=%%
          </td>
          <td>
            %%=v(@Package)=%%
          </td>
          <td>
            %%=v(@Price)=%%
          </td>
         </tr>
        %%[ next @i ]%%
        %%[ else ]%%
        %%[ endif ]%%
        </table>