How to get Pages to sort dates on charts like the original Excel file did

New iPad and Pages user. I grabbed an existing Excel spreadsheet and opened it up in Pages.

There's a data type column with the most recent dates on top. In Excel, the chart produced from this data would display the data information left-to-right, in the order as the column (from top-to-bottom).

Pages, however, is displaying the dates from left-to-right, newest to oldest - the exact opposite of the conventional left-to-right, top-to-bottom default display we're all used to.

How do I get my charts to display the dates in the top-to-bottom order I've listed them in the original worksheet?