Hello Jérome,
The approach that Antonio have suggested with the RadPivotGrid1.SetFilterIncludes should get you the desired result, but I have tested it locally for the Year and I have noticed that for some reason it does not apply the provided year to the Include collection:
If you apply the same to a String field you can see that it is working correctly.
I will forward this to our developers, so they could further investigate what could cause the issue with the Year field.
Please excuse us for any inconvenience caused by this.
Regards,
Konstantin Dikov
Telerik
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.