We have the same problem and it sorts via 01, 10, 11, 12, 02, 03 - 09
Accruals are messed up from formulas when you sort by employee as well.
I did some testing and found that this will happen if you your computer's short date format is set to a format that uses a single-digit the month, like M/D/YY, M/DD/YY, M/D/YYYY, or M/DD/YYYY. It'll also be an issue if using a single digit for day of the month, though less of one.
To get the report to sort correctly in all cases, change your computer's short date format to one that includes MM/DD - either MM/DD/YY or MM/DD/YYYY - and then restart QuickBooks if it's running (important), and then run the report again.
The dates should sort correctly after making that change.