Ssrs convert date to string

I have a table wit a date column which I want to arrange into columns for different years, Where do I filter columns?
I have tried to filter the details group withe the following expression:
=Year(Fields!Ontledingsdatum.Value) = year(now) -5,but get the following error :
Cannot compare data of types System.Boolean and System.String.
Also I think putting the filter in the details group is incorrect.
Regards