Jasper Report Server cannot filter..

Hi all.

I just want to ask something that really bothers me.

Everytime I reformat the data in Jasper Report, I cannot use the filter functionality.

Meaning I have the column title Year.

In the database the field is datetime format.. But when I display it,I reformat it to show only Year.

I noticed that everytime I made changes to the column data, I cannot filter it. 

Btw. I'm using Table components.

So can I know how can I fix this?

Thanks