how to clear up mixed date/text column
 

I have a column of mixed date/text in an Excel Workbook. The workbook
is downloaded from SAP system.

The column contains data that look like dates , but up sorting, they
would appear at different places; the "istext" function would confirm
they are text or data.

03/21/2006 istext = true
03/21/2006 istext= false

How to fix problems like this?

I tried:
a) format-cell - data - date for the column etc.
b) copy/special paste - text/value etc

but none worked for me.

Thanks for suggestions.