Hi David,
did you set custom locale for date format in the control panel?
Powerserver comes with default globalization params in the web.config, which may be different to the locale.
To workaround system settings, usually it is enough to specify an mask for your DW date column. Select the date column -> property -> edit -> set the editmask (or just the format) to e.g. 'dd/mm/yyyy'.
Best,
Marco