Date format not supported

```
What steps will reproduce the problem?
1.upload .xls file with date column as dd-mm-yyyy format
2.parse the file using excel reader
3.output as 43159.

What is the expected output? What do you see instead?
dd-mm-yyyy

Please provide any additional information below
when i open new excel and type the data and then upload,it will working fine.
But it showing error when upload the same file 2nd time.
```

Original issue reported on code.google.com by `evan.r...@gmail.com` on 4 Feb 2013 at 10:36

Attachments:
- [hi.xls](https://storage.googleapis.com/google-code-attachments/php-excel-reader/issue-164/comment-0/hi.xls)

Start by reproducing the issue with the attached hi.xls file: upload it, parse it with the Excel reader, and compare the date output on the first and second uploads. Trace the date parsing path and verify that the dd-mm-yyyy value is returned consistently instead of 43159 or an error.

Written by the indexing model from the issue text.