It has been a nightmare to convert number fields from excel to date fields in SPSS.
1. Select columns with dates in excel, right-click the mouse --> cell format --> number --> date --Choose format 03/1/11.
2. This format use / to separate the parts of a date. So, now select the column again and use Find/Replace to find every "/" and change it for a dot ".". Save again.
3. Open SPPS and import the excel file.
I have had no problem with this method.