it's not normaly to change the settings of a user, he/she have set them for some reson.
if you want to show them a date in your format use the format function
or if they have to give you input, trap the input and change it to your format or use a MaskEditBox with your desired format
But if you realy want to change it there must be some kind of API you can call (remember to reset them to his her setting, not every 1 uses the same format: USA: MM-DD-YYYY ; EUROPA : DD-MM-YYYY ; ACCESS : YYYY-MM-DD )
some comment using general settings :
When you enter data using locale-specific format in the Grid pane, the Query Designer automatically translates it to ANSI format in the SQL pane. For example, if your Regional Settings are set to Standard German, you can enter a date in the Grid pane in a format such as "31.12.96." However, the date will appear in the SQL pane in ANSI datetime format as { ts '1996-12-31 00:00:00' } If you enter data directly in the SQL pane, you must enter it in ANSI format.