Excel XLS file preview - wrong date (spanish format 31/12/2011)

Hello,

I made a XLS file on my MacBook which I uploaded to my Dropbox.

It happens the same if I mail the file and then I open it on Mail.

Since I open it on my iPhone the preview shows a wrong date, ie. instead of 31/12/2011 it shows 365/12/2011, instead of 30/12/2011 it shows 364/12/2011 and instead of 01/01/2012 it shows 01/01/2011

But if the date is 02/01/2012 or 03/01/2012 it is shown in a correct way.

Date format is DD/MM/AAAA (Day/Month/Year)

I have not installed Numbers, I use iOS preview.

Please check a XLS and a PDF preview to see what I mean.

Regards,

Jairo