To change your date format in OS X:
Close Brief Accounting then open your System Preferences. Select Date & Time:
Select Open Language & Text:
Select the Formats tab, then the Customize button in the Dates section:
In the Short section, drag and edit the date format so that it is as follows: M/D/YY:
NOTE: Format must be exactly as below. Uses forward slashes as separators rather than hyphens.
Click OK when done.
Relaunch Brief Accounting.