I haven't been able to find an answer to this.

I have multiple files that I use regularly in excel that now have cell formats of "date". Every single cell in the entire workbook (all sheets) is now formatted as "date". The problem is that I lost my formatting for percents, numbers years, etc and now everything is converted to date (xx/xx/xxxx).

I am able to open previously saved versions of a file (prior to me having the problem) and the cells are formatted as I intend them to be (percents, numbers, general, as well as dates).

Since this has happened on a couple different files recently, I am wondering how this is happening and how do I prevent it from happening in the future. I cannot cure the problem just by highlighting the entire sheet and converting back to general because I lose all my percents and number formatting.

Example (Correct formatting):

Month   Year    Working Days    MTD POS
        Curr    Rem 

May     2012    22  0    1,553,549 
June    2012    22  0    1,516,903 
June    2011    22  0    1,555,512 
June    2010    22  0    1,584,704 

Example (Incorrect formatting):

Month   Year    Working Days        MTD POS
        Curr    Rem 

June    Tuesday, July 04, 1905  Wednesday, January 04, 1900 Wednesday, January 18, 1900  213,320 
July    Tuesday, July 04, 1905  Wednesday, January 04, 1900 Monday, January 16, 1900     314,261 
July    Monday, July 03, 1905   Wednesday, January 04, 1900 Sunday, January 15, 1900     447,759 
July    Sunday, July 02, 1905   Wednesday, January 04, 1900 Monday, January 16, 1900     321,952 

Sorry for the mess. Any suggestions?