Feature request related to a bug issue I've sent:
https://support.zabbix.com/browse/ZBX-13429

> If I configure a tree of services the system will start populating the reports only from the moment i submit the tree itself, ignoring the old trigger data.

> I understand that this is the default behavior, which I think needs adjusting

Right now we have to define a Service tree and wait, we cannot work on existing data (ie: pas year's triggers)

I think that the Service report should have the option to read past data and calculate SLA service.