Pivot not responding

On cell A1 I have a date, let's say 01/01/2014. On cell B1 I have the fmla =Year(A1), with a "General" format, so it shows "2014" as the answer. I have this same inputs/outputs for dates that range from 2007 to 2014.

Today, for some reason, Excel changed the values of my column from numbers to dates. I changed them all back, but the pivot table linked to the cells didn't respond, and when I went to filtered my information by year, my options were dates: instead of the year 2014, the filter showed 6-Jul.

I tried to remove the filter, refresh the the pivot, adding the filter back again, moved the Options around: "Preserve cell formatting on up date", Data/"Number of items to remain per field: None/Automatic", and all possible combinations of these, but I wasn't able to restore the PivotTable filters the way I had them before.

Any help will be appreciated.

Hello,

Do you think it is posible for you to post a sample workbook?