SystemDateChanges

hi,
I am having a cyber cafe where i am using a cafe management software. Recently i was facing one problem, my client systems date were changing automatically but time was correct. Cafe manager support team suggested to set regional and language short date format as m/d/yyyy on server side. issue resolved with some of the systems. but still facing on some of the terminals. no issue with CMOS battery and system regional setting and time zone. Only issue occurs once the client screen comes up and connects to server.
Any idea……