User date format: When I use the instruction "Default F[BKPF-BLDAT] &[today_user]" the date is not in my SAP user format. Is there a setting to avoid this situation?

Use:

Default F[BKPF-BLDAT]  "&V[today_user]"

This is the date in the format chosen by the user, e.g. dd.mm.yyyy or mm/dd/yyyy (25.12.2010 or 12/25/2010).

Please note: You need a valid RFC user in the GuiXT profiles with appropriate permission to execute the function module "BAPI_USER_GET_DETAIL". For details see Documentation->GuiXT- >System variables.