Question : excel 2007 all numbers in spreadsheet converted to date unintentionally

This has happened to me several times.  I have a multisheet spreadsheet I work with every month.  It has lists of numbers in each spreadsheet. It was created with Office 2003 Excel but converted to Office 2007 Excel.  For no unknown reason, I will open the file and all of my integers have been converted to dates.  It is very frustrating.  I have different columns in the spreadsheet that have different formats, and I can't blanket the spreadsheet and each page to be non-date because I have some dates in there.  It would mess up all of my formatting.  Luckily I usually have a saved copy (before updates/after updates) that I can revert to, but this last month I didn't make the copy after I made changes so I lost all my changes.  

Does anyone have ANY idea why this is happening? Am I doing something wrong? The file looks fine when I save it but when I re-open it later, all my numbers are gone.

The spreadsheet takes a list of counts from last month and compares to this months counts and shows a difference.  There are many formulas in this multisheet workbook.

Hopefully my questions are clear .... Please ask if you need clarification.  I have searched and can't find anything on it.

Thank you!
Jeanne

Answer : excel 2007 all numbers in spreadsheet converted to date unintentionally

I found this possible solution:
In Excel 2007 you can click on the 'Cell Styles' option on the menu bar. Then right Click on 'Normal' in the top left hand corner of the displayed styles and then select the 'Modify' option. you will see that the number format is set to date and time.

Select the format... button and then select whichever format you want for general numbers, e.g. two decimal places and red for negative. Click on 'Ok' and you should see that the format in the dialogue box has been reset to '0.00;[Red]0.00'. Click on OK, and then save the spreadsheet. You should find that all cells now default to this format for numbers rather than Date/Time.