convert date format to dd-mm-yyyy


Is There any function module to covert date format.

I have tried an abap logic

when i am trying to download the report to excel  the date format should be change

The date 10-01-2012 in this case it is coming  perfect

This date 1-01-2012 in this case when i am downloading into excel it will come like this 1/1/2012

please give me some suggestions.

Best Regards,