clean up the object which on longer available

Hi everyone,

I wanna know how to clean up the object (user or computer) which on longer available .

e.g.

some people leaved or some computers were dis-commission but we didn't do anything on our AD. So there lots of invalid user and computer in our active directory.

is there has some way to clean up those objects?

for example, query out over 60 days not "online" objects, and delete it? btw, we have SCCM, if this can be done by sccm ?

thank lots

Jerry