Set V[g_test_date_field] "13/12/2003"
Set V[reldate] "&V[g_test_date_field]" - "01.01.1000"
Set V[g_test_date_field] "01.01.1000" + "&V[reldate]"
Return

GuiXT supports the following 6 date formats (same formats as are possible in SAP):

dd.mm.yyyy 
mm/dd/yyyy 
mm-dd-yyyy 
yyyy.mm.dd 
yyyy/mm/dd 
yyyy-mm-dd

but not

dd/mm/yyyy

since e.g. 06/07/2003 would then be ambiguous.

With "12/13/2003", your computation works fine.