See also https://support.datapa.com/solution/articles/36000029511-why-do-dates-show-in-a-different-format-in-enterprise-in-the-web-
Reports are PDF files generated on the server, usually in advance of viewing in the web. Dates will appear by default in the region to which the server is set.
To see dates in the reports in another date format, ensure the region of the server is set to your desired region. In particular, you should copy the region settings to be used by System accounts; this can be done in the Administrative Language Settings, clicking on 'Copy Settings' (screenshots below)
Please restart the DataPA Enterprise Service after doing so. You may need to restart the server also for the new settings to take effect.
The region in use by DataPA Enterprise can be confirmed by inspecting the latest c:\programdata\datapa\DataPAEnterpriseService.log. Search for the last entry for "Current Culture is...", which is written out when the service starts.
If you are unable to change the system region on the server, you may set the format of the dates in the report itself. Please see the following article on how to do this: https://datapa.com/help/date_output_format.htm